The thing that I've found that motivates me the most long term is to work on problems that I think are important to work on. Working on challenging problems is

The thing that I've found that motivates me the most long term is to work on problems that I think are important to work on. Working on challenging problems is great, and motivating for a while (few years), but ultimately I need to work on something that I think makes a difference in the world. Also something where I think that my skills can uniquely make a difference to the problem, but that by itself is not sufficient. I'll still get frustrated and demotivated at times, but I will come back to it with a feeling that I am at least trying to work on something important and challenging even when things don't go right or they get particularly hard. As an example, I spent a few years working on ASIC design for high def video encoding and decoding (HD-DVD and Blu-Ray). Super interesting and challenging. Wow I don't care about it's impact on the world though.