I guess looking back on things, my worst regret is triggering a chain of events that will eventually cause the destruction of the time space continuum itself.
I suppose looking at it positively, I could say that I was only another link along the inevitable path of destruction that started before there was even a time and space itself.
But really, by pushing a big red button marked "EVENTUAL DESTRUCTION OF TIME SPACE CONTINUUM THROUGH LONG CHAIN OF EVENTS - DO NOT PUSH", most of the blame has to lie firmly on my shoulders. I have to say, it wasn't particularly eventful though. I mean all that happened was some fly flew through the window soon after, which I swatted promptly.