what's your attitude towards the code you write? Towards the problem that happen to cross your way?
how do you live with the feeling of having problems all day long and need to solve them? (otherwise you get fired or whatever)

If I was solving the sort of large, depressing problem like "world hunger", I probably would get dragged down fast. Fortunately for me (though perhaps less fortunately for the people who are starving), I don't have to solve that sort of problem.

Programmers solve problems of a different nature. They are almost purely intellectual. Everything from a one-line Golf up to a major application is put together with a bunch of abstract problems that often have use in a wide veriety of tasks. To use a language effectively, you must know what sort of abstract problems your language is good at, and apply them as needed.

This, I think, is the primary difference between CS and pure Mathmatics. Even though computers have a direct relationship to math, CS needs to be more concerned with abstraction rather than mathmatical rigor (which in some ways are opposites of each other).

. . . often you know it should be that way but you can't be 100% sure . . .

Something tells me that even "gods" of programming can't do this one. It's not the abstract problems mentioned above that will get to you, but rather if the particular abstraction you applied is the best one for the real world problem you're trying to solve. At some point, you have to get real work done, and you have to go with a solution that you may not be comfertable with because you don't have a better one.

On dealing with burn-out: a few months ago, we had rolled out what is probably the largest system we've done (not huge by many corprate standards, but very large for only one coder (me) to create). Many users misunderstood the system (many of our users are older university professors who aren't comfertable with computers), and for almost a month straight I had nothing else to do but deal with the problems these users had. I would come in to work in the morning, read my e-mails of all the latest problems, fix each one in turn and send an e-mail back. By the time I finished with the last round, a new round would have come in. I was very close to complete burn-out during this time.

A solution I found was that during my break period, I would find a very calming peice of music. (My personal favorite for this is "Collean Dahs". Pachelbel's Canon also works well, if you get a good arrangement). Plug in the headphones, shut out everything else, close eyes, and focus on the music. When it's done, I am so completely relaxed that I can hardly open my eyes again.