Today was such a day... spent roughly 4 hours bug hunting. And at the end all I did was remove one line of code in one project and changed order of some statements in another project and now - all issues gone (for now).
These issues have been there for weeks, if not months, and it feels good to know that they are resolved now, but I don't really feel productive spending my whole day changing like 15 lines of code.
But hey, those 15 lines of code held me back for weeks, now I can continue! \o/