One thing that's very helpful for me is to always assume the best that makes sense in relation to whatever I know about the situation. When Simon, who is 2.5, acts in ways that seem inappropriate, this is pretty much invariably because some of his needs haven't been met, especially his need for sleep.
Another thing: I tend to have a long thought process when conflicts arise, which gets me out of thinking: "Oh my Gawd, this is SOOO annoying!!! I've GOT to get him to stop this NOWWWW!" Instead, I'm thinking things like: what need is he trying to meet by doing this (kicking the wall repeatedly), does it really matter, has he had enough sleep, how can I help ensure that he gets more sleep tomorrow, maybe we could spend some time playing, and so on... Actually telling Simon "We have a conflict. You want to kick the wall but that is making a lot of noise and it hurts my ears, I also feel that we should be gentle to our house. Could you please stop kicking the wall? Let's find something to do that works for both of us. How about X?" He's so cooperative when his needs are met, I don't really care when he's having a hard time with things (in the sense of thinking that I need to fix him). I just think that he's learning these things slowly, as they are hard to learn, so that of course he's going to have problems when all systems are not functioning at their finest.
Interestingly (to me), he can read a few words now (he's just memorized how they look). When asked to read them, he got the words right 100% of the time for over a week. The other day, though, on Thanksgiving, we thought that since it was a special day we'd have some greasy chemical-laden chips and some soy ice cream. He has no issue with soy, but the chocolate, sugar, and chemicals from the chips were not good! He wasn't in a bad mood, but he was a bit manic. He could no longer read the three words he had never gotten wrong. He was still a bit off the next day. The following day he was finally back to normal and hasn't gotten any of those three words wrong again. I really think that when the skills that we have are so fresh, it doesn't take a lot to make them out of reach, especially for very young children who are so enthusiastic and life and whose emotions can be so strong.