I have a close family member who struggles with a massive, childhood-abuse related guilt complex. This individual also has difficulty with an occasional hot temper and some nit-picky behavior as a result. I want to break down the cycle of faulty assumptions and belief systems that have arisen in this loved one, because it's occurred to me that they're quite common.
1) The belief that having any needs or wants of others isn't merely an inconvenience or burden --it's a shameful crime and evidence they're a bad person. (Of course, it's always normal and acceptable for anyone else to have needs/wants.)
2) The belief that continuing to have needs and wants in spite of #1 will drive others to hate them.
3) Because of #2, the deep fear or belief that others do in fact secretly despise them, or are fast coming to resent them.
4) The belief that in order to avoid #3, they must be continuously useful and super generous to make up for their inherent badness. Boundaries are hard to come by or maintain. Honest communication shuts down, and they do their best to stuff any difficult feelings.(People-pleasing/ doormat/ fawning behavior.)
5) As a result of the emotional exhaustion caused by #4, the resentful feeling or belief that no one puts up nearly the effort or care they do may set in. There's a small element of truth to that, because constant people pleasing to make up for one's own perceived unlovableness is typically excessive and unhealthy. Showing love and kindness through helpful actions is great, but it becomes poisonous when the motive is fear or a sense of inadequacy. The terrible irony is that part of why others aren't doing as much for them is often that they continuously turn down most offers and efforts on others' part to show mutual kindness.
6) Between the belief that others harbor secret hatred and the feeling that no one else is putting in an similar effort, they start to feel used and offended. They project their negative thoughts and ideas about themselves onto those they're trying to please or even those they genuinely care for, such that when the guilt hits really hard, it feels like an attack from those other people.
7) Because of #6, conflict occurs. When things finally settle down and everyone's brought to the point of stating their true intentions, they defeatedly admit they took something personally or misunderstood it because they were feeling guilty. Their guilt warped their perception of others' thoughts, feelings, intentions, etc. into something much worse than was really going on.
8) They feel deeply ashamed over having caused unnecessary conflict or a heated misunderstanding, and double down on their guilt because they feel they deserve it. Self loathing increases. The incident of conflict then serves as "evidence" that people not only secretly hate them, but that they do so with good reason. They may very much want to believe it when others reassure them they're not hated, but it feels too far fetched to be true.
9) They attempt to communicate their needs and concerns better for a bit--and may even do a very good job of articulating their feelings for a short while-- but their guilt and shame quickly stifles or complicates those efforts, leading back to #1. They may shut down somewhat, and grow defensive of keeping their more "inconvenient" emotions under lock and key. Unfortunately, without recognition of the overall pattern and cycle, this behavior might seem to others as normal boundary setting.
There is only one point at which this cycle can be broken, and that's #1. I strongly dislike the notion that we teach others how to treat us, as it absolves those others of responsibility for their own actions, but how we see ourselves does inevitably impact how we relate to others, and how they in turn respond to us. People can only work with the information they have, and unresolved or unmanaged guilt complexes drive so, so much misunderstanding and needless conflict. However, it is impossible to guilt and shame oneself out of feeling guilty and ashamed.
Trying to think of oneself in a positive light might be too much of a reach to start, but anything is better than believing oneself to be fundamentally bad and wrong. A place of steady neutrality is a good starting point. "I'm a normal human being having normal human feelings, with typical human needs for support," for instance, is far preferable. It doesn't demand cheery forced celebration of oneself, but also represents a marked move away from the kind of self-denigration a guilt complex thrives on.