While others suggested only doing one side project until completion (which is an overall good strategy), I know the feeling of having tons of exciting ideas/side projects that you just don't want to completely put aside. My strategy has made some compromises on the overall completion date, but scratches the itch I have to work on different projects.
Basically, I spend one month focusing on a single project so that I get good mental focus for the month and then am able to feel like I'm still doing multiple side projects in a reasonable amount of time. Additionally, when I come back around to the same project a few months later, I have a fresh perspective along with some (hopefully) new skills or skill levels. That's how I find a balance.
Per day, I basically just work however long I feel like it. If I have plans with friends or want to work out or something I just go do it. Makes it low pressure and let's me make sure I'm always enjoying doing my side project work.
