How easy we forget...

Why is it so easy to forget the difficulties that we left before any discomfort we have currently?  As I know many people struggle with, I've had some difficulties with the uncertainty of my life at this point.  I'm busting my butt to get my name out there as a drummer and arranger/composer in Nashville since I moved there, but I still feel uncomfortable about the uncertainty of working as a self-employed musician.  I'm not sure where to go to get more consistent work.  But when looking back at when I was doing a big-boy job at a office in Manhattan, many of the days I spent there felt like such pointless laps in this hamster wheel where you just keep on working and working and the work never ends.  It was very frustrating and I was ready to walk out of the job multiple times over the last few years.  I was getting super frustrated with having to work so much without having the ability to work for my art of try out what might happen with the talents I have cultivated over the years.  Now that I'm in that position to try to figure out what I can do with that, I feel anxious about the uncertainty of not having a regular day job.  I see it as a difficulty with a "grass is always greener" paradox, where no matter what I do, I'm always struggling with wanting what I don't currently have.  How do you work to move away from that and just learn to be happy with the gifts in your life that you currently are enjoying?