What exactly makes a hobby a stress reliever? I have been running this thought through my head for a while now. During the semester I have noticed that I pick easy projects to work on. Does this help my stress relief?

For myself, yes, I think so. There are moments during the semester that I feel hopeless. That no matter how much I study, I will never learn a concept. Does anyone else get that feeling?
When this happens, I assume it’s stress telling me this. For stress is the fear of not being able to complete something, and that is definitely something I feel while trying to learn.
At those moments I take a deep breath, and walk away from what I was working on to do a crafty or artsy project. I think about the concept while I work, and try to connect the links I do not understand. When the project is done, I usually understand my concept a lot better, at least enough to where I am able to get on with my studies.
So I guess what makes a hobby a stress reliever is one that helps you solve the problem giving you the stress. A hobby that gives time for you to walk away from whatever is giving you stress and come back refreshed. They say that your brain works on a problem even when you’re doing other things. Maybe this is why hobbies help with stress.