Sometimes you don't realize how many thing are giving away for those side projects. With those side project don't make you any money, they are pure leisure you should see it like 'playing video games'. When start to refuse go out with friends or make simple home tasks to keep working in this side project, it becomes serious... Of course, those side project allow you to acquire or improve skills which may be useful in your professional life. But the way you balance it is very important.

The analogy of 'playing video games' should help you to see how serious and important these projects are to your life.