* Contributing to a project/mission that feels worthwhile.

* Practicing good craft/professionalism. (Which doesn't necessarily mean always being able to do the best code/architecture/process, but to work well within your constraints.)

* Being part of a good team.

Though ideally you have all three, and perhaps other things, as well.

I agree about abstract, and maybe that ties into feelings about contributing. For a while, I was working with only code related to aviation, and I felt good about my modest role in some good processes, but I don't actually like flying, so I hadn't been up-close with airplanes in a while. One day, it occurred to me that it would be a boost of inspiration to go see some of the real-world aircraft and activity. Aviation is really amazing concert of processes and technology, most of it not visible, but there's something to be said for tangible. Since I wasn't aware of anything like an observation window in my airport that (post-9/11) one could access without a ticket, I spent some time finding and printing photos of some of the aircraft I'd been working with, and decorated my office, which did give a boost.