This was a big one for me. I was 34 before I was really happy in my job. In my last job, someone asked "How did you get a job at age 65?" I told them the job looked like fun and the first 12 people failed the programming test.
However, just out of college I wanted to apply my math degree. My first project, writing an app to solve 40 equations with 90 unknowns, was frustrating because it took 2 months longer than I expected (management budgeted 8 months longer).
Although every project for the next 7 years was successful, none met my expectations out of college. I took 3 years off doing something unrelated that did not need a degree.
Finally, I reviewed my work history, identified what I enjoyed the most, and went back into the work force doing that until age 70.