The answer? Me.
The things that had been dragging me down—fear, guilt, regret, anxiety, sorrow—were so persistent because my primary response had been to wait for them to change. All my problems would go away if I held on long enough. External forces would eventually assert themselves and alter my situation for the better. This, coming from the control freak. No wonder I was so frequently unhappy.
In the last few days, I've adopted the "Do Something About It" policy: if it bothers me, do something about it. I have the power to wash dishes when I'm tired of looking at the pile next to the sink. I am capable of spending less money so I don't feel so paranoid about my cash flow. I am not required to work on my creative side projects when I honestly don't have the time or drive to do them right. If all it takes is a minor inconvenience in the short term to stifle an issue that'll bug me in the long term, then I'll feel better doing something about it instead of gritting my teeth for days or weeks or months on end.
The "Do Something About It" policy extends beyond the realm of physically doing something, too. Many of the things that annoy and depress me are beyond my ability to change, yet it's up to me whether I allow my negative feelings about them to take me hostage. Does the motorist who fails to use his turn signal really deserve more than a few seconds of righteous frustration from me? Am I a better person for only ever getting sad when I think of my deceased relatives, as though their absence is the only thing worth remembering about them? I lose more than I gain when I dwell on my aggravations and sorrows. Acknowledging them is one thing, but there's a certain point when it's no longer productive—if not outright counter-productive—to focus on the negative.
That's where I find myself now: identifying when it's no longer productive to focus on the negative. Whether by thought or action, I'm making my life a happier one. It's the best I've felt in a long time.