I think it is kinda strange but I just noticed that I have this odd habit of feeling tired, sleepy and dizzy when I encounter a (programming) problem that I can't solve after a while of trying. It generally shows up when I'm dealing with svn, reading someone else's code or resolving regression issues (old bug reappearing again).
To my understanding, this has nothing to do with being exhausted or tired because I just felt brilliant like 30 minutes ago and now, after 30 minutes of wrestling with a problem that I can't (apparently) solve, I suddenly feel an urge to go to sleep. And I really can go to sleep when I feel like that. If I shift my focus to something else or just leave it, then after like 10 minutes or so I feel normal again and am ready to continue.
I finally managed to talk about it to a colleague who sits just next to me and he sometimes feels the same way in some extreme cases of constant failures and he also finds it strange and new but there is another person who sits a little farther but he isn't feeling anything like this when he encounters difficulty
EIDT: I realized the fear of failing the whole project seems to play an important role. Since I'm the agile manager in the team, when I face a problem I can't immediately solve, subconsciously I start to tell myself : this is gonna make the whole thing fail. Specially when regressions happen.