Equanimity is a protection from the eight worldly winds: praise and blame, success and failure, pleasure and pain, fame and disrepute.
Guilt can be seen as a combination of self-blame, failure, pain and maybe disrepute too.

I'll assume most people will immediately see how guilt is pain. It usually arises from a failure (if not a failure to do what one selfishly wanted, at least a failure to hide a selfish deed… a failure to maintain one's reputation, to one's own eyes and to others’). It naturally comes with a mental fabrication “I could/should have done different” (with a judgmental tone rather than an ‘objective’ assessment).

What one might need to enquire into though is not so much the current pain, the current dissatisfaction. This only needs to be answered with compassion, loving-kindness, patience… What one might need to enquire into is how to avoid the perpetuation of guilt.

For guilt has a strong propensity to perpetuate itself, for long. A classic case for the perpetuation is simply to punish oneself on and on, to cling on the guilt so that no remedial is good enough, no apology is good enough, no pain is enough to ‘pay’. The punishment loses any connection with the notion of proportion.

염불서승 (Old Buddhist Monk Praying to Buddha), © Kim Hong-do (1745–1806)

Another classic case for the perpetuation of guilt is the « trying to create something worth the bad we feel guilty of. »

It is common because we're inseparable from a web of impermanent relationships to the world but, out of ignorance, we easily project permanency of some/most relationships and therefore supposedly ‘commit’ forever. Then we find ourselves breaking such a commitment, becoming ‘traitors’ and ‘disappointments'…
Examples could be: committing to particular studies, only to later want to do something else with one's life… committing to a particular relationship with someone, only to later want to commit elsewhere (possibly another relationship but maybe simply another cause, another lifestyle)… committing to specific beliefs, ‘values’ and ‘principles’, only to later find them inappropriate and questionable… committing to a project methodology, only to later find it over-kill or unable to scale…
Abandoning the initial commitment might prove painful (by how you perceive yourself, as well as by how the environment responds to the ‘betrayal’) but the perpetuation of the guilt might arise from the next commitment!
Examples would be: going “all in” when changing career, investing all you've got, without any step back, without wisdom, without adaptation to the context's response, simply trying to force a successful change of occupation, trying to prove that the betrayal was worth the pain because it led to success… struggling with a new relationship beyond reason, simply trying to force a successful relationship, trying to prove the betrayal was worth the pain as it led to success… blinding oneself with new beliefs, ‘values’ and ‘principles’, no matter how impractical or senseless, trying to prove the change of faith was worth the pain as it led to some superior Truth (with a capital T)… Basically, the next commitment might be a —mild or not so mild— form of fanaticism, due to the guilt from changing a previous commitment (which was projected as “forever, in good times and in bad”).

Freedom is not found in ignoring causality, doing whatever you want as if no constraint applied, no hard lines existed in the (physical or social) context… Freedom is in freedom from biases, not letting unexamined impulses and erroneous views or even preconceptions bias your decisions.
When perpetuating guilt by trying to make the more recent commitment worth the exit from the previous one, you're biasing your present decision process by dragging the past as well as preconceived views on its meaning.
For example, you might be projecting that the exit might have been a mistake (e.g. a precipitated decision, or a case of ignorant impulses that took over wisdom…), but also that the ‘mistake’ could be turned into an acceptable, reputable ‘investment’ if only you had success now. ‘Mistake’ and ‘investment’ are projected meanings, they're interpretations to fit the worldly winds, to reassert the ego, to reassure yourself that you exist somehow independently and that you're in control… Or you might project that one mistake is acceptable, but no more…
Biases, i.e. ignorance, in decision processes usually lead to inappropriate responses to the circumstances at hand, hence to more dissatisfaction, to more clinging/aversion (more/other biases), and ultimately to another cycle of suffering… For example, guilt from past discrimination against others (racism, sexism, etc.) might lead to later fanatic acceptance of everything others want, an over-compensation rather than an appropriate response tailored to what is asked: “White guilt” leads to biases in the form of unconditionally accepting other ‘cultures’ and ‘traditions’ (FMG in the name of multi-culturalism? Really?), etc.

Hoping for success is already a recipe for saṃsāra, but embedding it with higher stakes out of guilt is increasing the probability of quick karmic negative feedback. It could theoretically be harnessed in order to learn fast (and I do mean “learn”, not just “call it ‘lessons learned’ then forget about it”!)… but it usually only drives people to “double up”, to become stubborn, to cling to ‘prove’ they're ‘right’!
The guilt might then unfold for years, claiming ‘perseverance’ and ‘patience’ where there's ‘stubbornness’ and ‘blindness’, claiming ‘effort’ or ‘generosity’ where there's ‘clinging'… The biases go as far as presenting defilements and unwholesome, unhelpful views as wholesome, perfected qualities (e.g. « confusing the distinction between ‘giving’ and ‘giving in’ » was mentioned in Get Out of the Guilt).

The “four immeasurables” are key to let go of guilt: compassion and loving-kindness should benefit all, and ‘all’ is inclusive of ‘you’.
Part of letting go of guilt is to acknowledge that 1. you were mistaken when you committed initially (e.g. naïvely hoping that this specific commitment would bring lasting happiness) and that 2. human make mistakes.
Blaming victims is never constructive (it's too late for the ‘right’ advice “in hindsight”…), and blaming victims of their own ignorance is no different: empowering oneself not to make the same mistake might make a difference, might prove constructive and wholesome, but blame and guilt are unnecessary (there's no ‘need’ to suffer in order to learn: enthusiasm is a more effective motivation! No one becomes truly good at something they hate! Carrot over stick, aka. “expedient means”).
So, be compassionate toward yourself and your past mistakes. Learn the lesson (don't just file it under the “lessons learned” oft-forgottten folder) but don't carry the past over: not all ‘lessons’ should be kept, because some lessons no longer apply as the context is no longer the same… Forgive and forget!
Lessons are about causality, about tendencies, about how phenomena unfold (e.g. how guilt unfolds), they're not about ‘people’ (a fast-varying complex of impermanent aggregates of inconstant views, moods, sensations and emotions), they're not judgements of one's “worth”.
You don't need to “make up for the past” (notably, having ceased a previous clinging doesn't ‘justify’ a new clinging —the primary root-cause of suffering!), you only need to be free from biases now, see things as they are now, provide the appropriate response to the present circumstances.
You only need to embody wisdom now; the past cannot be changed, and spending energy to re-narrate it differently is pretty much a waste of resources you could put to better use.

There's a limit to “lessons learned”. Overcompensation is a risk which looms large. Moreover, appropriateness (in hindsight) to the past does not imply appropriateness to the present. But, most fundamentally, clinging to ‘lessons’ as to a truth might be as nefarious as clinging to ignorance: