In a way, you are semi-correct. Convincing in simple terms means that you believe in what yousay/feel/think and you make others confident in what you say/feel/think.

not really. when you use the word 'convincing' to describe smth or smn (people, for example), you mean that their speech and actions are so good that they can convince you so, "a convincing example" is a good example that you believe in and you are sure OF things and people can surely be convincing also

想表达“我确信”是吧？那就是I'm convinced. I'm convinced, because something/someone convincing convinces me. 跟excite， interest，annoy那些词一个道理， I'm excited, because something/someone exciting excites me. 用ed还是ing，跟人还是东西无关，是要看主动还是被动。convince是“使确信”，因此你是被convince，所以说You are convinced.

I like your explanation. The last sentence you said makes everything easier for me. Also, the meaning of 'quite' matters a lot. (And I understood it wrong before. But now I know it :) The best answer.

Here, whatever haopened clearly does mean something ; probably something bad for the speaker. So his speech is idiomatic (the perhaps unexpected use of the present continuous is often a clue), and he is saying (I'm doing it too :)) to himself that whatever it is, it really doesn't mean anything. "Pretty", here, means, "fairly", or "quite", or "somewhat" or "a little" - but not "very" or "completely". So, he is trying to tell himself that something does not matter. But he is not really convincing (or, you might say "fooling") himself.