This isn't a saying per se, it is a way of saying that has had an amazing effect on my attitude towards everything in my life.
Instead of saying: "I HAVE TO go to work" (I have to do this or that, whatever this or that may be) say: "I GET TO go to work." (I get to do this or that, whatever this that may be)
When I learned about this simple change in wording, I was surprised by how many times I would say, "I have to..."
For me, saying "I get to..." instead puts me in a good state of happy anticipation instead of a rueful, sighing, "now I must" state of mind.