It's been a while since I worked on a canvas. I tend to have a rush of inspiration that dies quite quickly then I'm onto something new but I am finding as I go on (down to age/experience/maturity/laziness perhaps) that now I am able to stay on the same path and keep developing. I don't panic when I come to a dead stop because I know it's time to go out and look for new inspiration that will allow me to continue and stay fresh without feeling like a failure. Or a fraud. Or going out and working for a supermarket instead.
This particlular piece I have been working on for a year now and finally it is finished. I have 5 brand new ones on the go too, they may be completed soon, they may not.
It's good to let go, you should try it sometime.