Sometimes I have all sorts of time to quilt--an unusually free weekend, or a random day off from work. But that rarely happens-- usually I don't get blocks of time. So I try to work on the "10 minute" rule. If I have 10 minutes free, I do 10 minutes worth of quilting. For example, I've got a wallhanging I want to get done by Thursday as a gift (well, good luck with that). I had almost no free time this weekend but I took 10 minutes here and there to get all the fabrics pressed and ready to go--so when I get my planned hour this afternoon I'll be ready to get to work on it.
I am fortunate enough to have space to have my sewing area set up at all times--and it's in the same room as my home office where I work full-time from home. So if I've got projects in the right stages, sometimes I'll do 10 minutes at the beginning or end of my lunch hour, or 10 minutes while I'm printing off a project or waiting for something to upload, etc.
There are times when it's nice to go slowly, but I also need the finished projects as reward on a regular basis. So I have some projects that are in process and are a little more challenging, taking a little more time (those usually get worked on when I do have random chunks of time), but I also have some faster projects on the back burner that if I only have a few hours and am jonesing for some results that I can show off to friends and family I'm ready to go. I also have projects in stages that can be worked on in different settings--those that need my sewing room, but also those that I can be working on while hanging out with the family watching TV at night or whatever--such as sewing the binding on.
It just takes some forethought and a little bit of practice to get into the swing of how to be as productive as you choose to be. Plus not having overly high expectations of yourself. I think most of us have ten thousand projects we'd love to be working on!