In order to accept one's self, it is necessary to know one's self - which can be quite a task, and also a paradox - if one doubts themself, how can they accept what they might learn? Logic, feedback from others, intuition, studying, emotions, and other sources can all provide various (and conflicting) information.
Ultimately, though, to accept one's self, one must take a risk in choosing to trust and believe their own judgement, knowing that it might not have ideal outcomes (though not necessarily the most undesired ones, either). It may not be easy, and psychological conditions can affect certain aspects of striving to achieve this.
This being said, what one learns about one's self may not always be what they want - sometimes these aspects can be changed, or improved, and sometimes they cannot - what is important, however, is that they be accepted, as they are a part of one's self; otherwise, by rejecting them, one is rejecting an aspect of who they are.
Self-expression is very vital to self-discovery, be it in one's actions (including volunteering), body art, words, acting, wardrobe, or other ways. In addition, such actions can help give one goals and a purpose to focus on, with significant results; self-expression involves showing and presenting one's true self - not necessarily to the whole world, or even necessarily one's closest individuals - sometimes, just being open and true with one's self about something can be enough.
Please note that the following sources are not being presented as certified in art therapy.