It creeps in, sometimes, and sometimes it is with reason at others without. In my case it is not so much dejection and hopelessness it is anger at self for procrastination and for finding excuses to blanket over my shortcomings and bad decisions. Hindsight is terrible unless it is consciously made to work in one's favor by extracting only the learnings and not letting the bitter tastes into one's brain, leave alone the stage where one has to "spit it out". It takes some doing. It's got to.