illustration (attribution, if any possible, is at the end of the article)
Desires are not automatically a sign of repeated ignorance, a sign of tendency, of bias. Desires are thoughts, and thoughts are just conditioned phenomena.
Some desires may be conditioned by a 'tendency' (i.e. karma), maybe a tendency so strong we'd safely call it an 'obsession'; this can be 'educated' thanks to mindfulness, cultivation, sticking to the path and to precepts… But some desires may also be conditioned simply by new 'opportunities'. For example, technology regularly offers breakthroughs, and offers new "objects of lust", that no one in a previous life could even have imagined. Nobody could want to e.g. "know other cultures", when no 'culture' yet existed in prehistoric times.
New circumstances in life constantly arise: the 'cyclicality' of karma isn't contradictory with 'impermanence', the tendencies simply face new conditions… As the tendencies co-dependently exist with the context at hand, some new tendencies arise, some old tendencies cease (this is part of 'cyclicality' too)! An individual's karma itself isn't constant!
You might identify your 'generic' tendency to project a "greener grass next door" fallacy on such new objects (this might explain partly why some people so enthusiastically update their mobile phone constantly… if it's not just "to keep up with the Joneses"), but that's abusively twisting the teachings if you forget that the projection is tied to specific objects.
You might have a tendency to crave 'fruits' in general (e.g. for their sweetness), but you didn't yearn for pineapples if you couldn't imagine them. And the moment you're presented with a 'new' fruit, you might wonder whether it will be comparable to other fruits you know, or if it will be "the exception to the rule"…
That is to say: you won't automatically crave what you don't know, you'll crave only what you project to be similar to something specific that you know and like. If you don't perceive enough resemblance to make the projection, you will adopt a "wait and see" attitude (or even a 'skeptical' attitude, an aversion to change) rather than crave.
You remember that nirvāṇa isn't "another place", right? This is true for Theravādins as well as for Mahayanists.
In Mahāyāna terms: saṃsāra is nirvāṇa, nirvāṇa is saṃsāra. So what makes "reality" be either saṃsāra or nirvāṇa? The way we relate to phenomena!
When we cling, when we have views (and project them, i.e. cling to them as if they were truths), we're experiencing saṃsāra… When we "see things as they are" (without biases, tendencies, prejudices, preferences i.e. without clinging), we're experiencing nirvāṇa. Same total reality, different way of relating to it.
Thoughts / desires are conditioned, they co-dependently arise with the context… and as long as you live in human form, it's bound to happen… but you have a choice on how you relate to each thought! How you relate will make the thought a cause of unsatisfactoriness, or not.
Guilt is a specific way to relate to a thought, but it's not a particularly skilful way. So you can drop the guilt, and still 'act' the appropriate response to give to the thought at hand. Guilt only brings bias to the equation, not wisdom.
Guilt usually arises when you "fell for" a desire earlier (this life, or another but the lesson has been passed down to you), when you consider you shouldn't have fallen for it (you learnt the associated suffering —to you and/or to others— now, so in hindsight it's easy to form such an opinion), and when you are reminded (immediately or much later) that it happened, that you were ignorant, that you were blinded by clinging / craving and didn't see the consequences its pursuit would create.
Guilt might also arise in relation to new desires though, if you don't understand that new desires can arise: if you have the wrong view that "all desires are repetitions", then any desire is perceived as a repeated temptation, i.e. as a lesson not learnt, as a proof of ignorance, as a proof of stupidity. The arising itself of a desire becomes painful (instead of simply a phenomenon to 'see' rise and cease); and this (guilt) is an unwise way to relate to the arising of a conditioned phenomenon!
Guilt is even trickier than that, because it is self-based.
By 'accepting' the guilt, you give yourself permission to fall again: "Oh this is me, I'm weak about this desire, nothing I can do to resist", or the classic "Oh, might as well, I'm going to hell anyway, I'm a bad person!"
By 'rejecting' guilt, often you reject responsibility (and thus cannot amend what you contributed but now deny you did), you tend not to let go of guilt but instead to carry around a fear of guilt itself (constantly thinking that " I hope not to experience this guilt again"… perpetuating the guilt as a "reference point" and an object of aversion relevant to your story, your preferences).
Guilt is an unwise way to relate to the arising of a conditioned phenomenon! A sense of humour is a lot more promising ;-)
[related: "regretting our failures" gplus.wallez.name/D2sNmccKcA8
and "forgive and forget" gplus.wallez.name/RdCyz2fTWJG]
Karma is not deterministic (causality is context-dependent: several conditions must be met for any effect to arise, and changing one's conditions does affect how causality unfolds… which is the key to karmic 'progress' towards "higher rebirths": by following the path, we cultivate circumstances that will be supportive and in which past mistakes will not condemn us to cyclical suffering, to repeated mistakes). Moreover, not all causality is related to intentions, but karma is related to intentions only (killing inadvertently an insect while walking explicitly is karmically-neutral; it isn't without causal consequences though!). If karma is not the sole causal law, it cannot be deterministic: other causal mechanisms might create new circumstances. Karma might bias how we perceive these new conditions but a bias isn't all there is.
New desires do arise (as the context changes and you can indeed imagine new 'objects') and they constitute new opportunities for you to relate (wisely or ignorantly) to the thoughts.
Desires might thus be "tests" of your recent evolution, rather than testimonies of repeated mistakes.
So, here and now, without tying (anchoring) yourself to past errors, freeing yourself from the past ignorant 'self' you imagine as your identity, without obsessing that only 'your' 'own' 'karma' control which desires 'you' experience, how will you respond? How will you embody Wisdom? Can you see how events will causally unfold from your intended response in the specific circumstances at hand? What is the appropriate and wholesome intention to manifest here and now? What will reduce dukkha for all sentient beings?
Image: "meditation" © Max Sauco