There was an article a while back about how time doesn't convert directly to money, at least in terms of an hourly wage.
Unless you put yourself in a situation where you can work any time you want, and earn hourly incremental dollars.
I was working two contract jobs at the same time, as I transitioned from one to another. Both sides had an attitude of "give me as many hours as you can". I did a lot of work, because making X dollars and hours usually seemed like time better spent than what I would have otherwise done.
It's hard to manage that kind of situation, but I should find at least something similar - some kind of project or side business where the money was fairly linear and incremental with time.
What jobs were these, and did they pay well? (Of course, feel free to not answer if you're concerned about privacy or similar.)
Another gem from xkcd: Is It Worth the Time? It visually answers the question:
Of course, he's not the first person to ask this question, but the visual is handy. Note that the times are calculated assuming you'll save the time over five years.
For example, I've been pondering how to shorten my showers. If I can shave off 1 minute daily, I should be willing to invest up to (but no more than) an entire day to do it. If I think I can shave off five minutes preparing my breakfast, I should be willing to spend up to six days attempting to do so.