When considering this topic I think one has to contend with the notion that suffering and well-being can't carry symmetrical weight.
The idea that they're not things you can combine into one value with the hopes that the sum ends up being positive. That in fact suffering just exists in the negative domain of qualia, and no amount of positive qualia can "cancel it out", unless the two are experienced simultaneously (in which case I don't think I'd consider that to be actual suffering).
I'm currently undecided on the merits of antinatalism for a variety of reasons.
That said, I have past experience of at least ten years of excruciating major depressive disorder, (doing much better now). If I were given the option to experience another decade of that, in exchange for an extra century of pain-free euphoria, I would absolutely decline that offer. Even if there were only a 10% chance that I'd even experience that decade, I would still decline.
Introduction
Antinatalism is the position, or class of positions, which finds existence is not preferable to nonexistence and which tries to minimize the creation of new people who will then suffer. I found it through David Benatar's book Better Never to Have Been, although I've encountered folk versions of it that are limited to certain conditions - why have a child in this blasted heath of a world? Benatar's deeper position, as I understand it, comes from counting positive and negative utility separately; nonexistence lacks any pain or suffering and is thus preferable, even if it involves no positive experience. (Even better, whatever negatives you would incur from "missing out" on positive experiences would be moot - there's simply no pain.)
A related position is efilism, taken from "life" backwards, the more fringe belief that life itself is suffering and that the only moral action is mass suicide. This is Dark Side philosophy if I've ever heard it, the girding with thought of one's most self-destructive impulses, possibly even a thought hazard. But I think that there's a way to redirect it, and what it represents, into doing useful ethical work without trying to burn the world down.
Fracturing Ethics
At least some minds can be broken up into bags of psychological subagents, and I think all minds can be expressed as cooperating with themselves (or failing to) across time. A person at time 0 is not the same person as at time 100, and certain of these subagents can clearly voice a preference not to exist. It's also possible to mix them, by saying that one subagent is more or less "in the driver's seat" at a given time, making up the circumstances under which this feeling of wanting-not-to-be arises. A person in extreme emotional distress will find more situations horrible than they would at an emotional baseline, and so they should seek to minimize states like distress and situations that are sufficiently negative.
This is all pretty instinctive, of course. The experience of pain or suffering seeks its own annihilation - we draw back from the flame and we flinch away from harsh realities. When we're in a terrible situation, typically we want to be anywhere else, or anyone else. In other words, some instances of ourselves would rather not have been brought into existence, and if at all possible would like to be replaced with other, better-adjusted instances. (By corollary, there are also some versions of ourselves that would enjoy existing very much, and we can navigate through these spaces of possible selves using natalism just as easily.)
This becomes a more utilitarian calculus when it's clear that cooperation is necessary between agents; smaller pains must sometimes be endured in order to avoid larger ones, forcing yourself not to flinch at reality is necessary to improve yourself, and so on. The goal here must diverge from Benatar's at least in that we minimize selves that don't want to exist instead of preventing them all from existing in totality. However, given the uphill battle an antinatalist or efilist faces, I think this program offers a better deal - more of what they want than they'd get otherwise.
Two Objections
First, this is essentially restating what we already intuitively believe in slightly different language. I think this is a fair characterization, and possibly these philosophies don't represent threats that need diverting this way. All I can say is that refocusing very self destructive ethics to perform more mainstream-ethically useful work seems worthwhile to me.
Second, the usefulness and intelligibility of this as a solution is tied to its granularity. If each day we're awake is considered a subagent, terminated by sleep, then this becomes an argument toward taking naps in the middle of bad days and hoping you're more well-adjusted afterward. If every second or minute of our existence is taken as a unique individual, then concepts like cooperation and suffering can begin to lose coherence. Ultimately, it's an abstraction, and cutting people into subagents is mostly useful in the moment when thinking of yourself as cut out from your past and future.