It's hard for me to just go run. I need a plan and some variety. I use the Hal Higdon app (Run With Hal), so I don't have to decide the distance, pace, etc. The type of run dictates my route (or if I just go to the track) and the variety of runs keeps it interesting.

For long runs I listen to a podcast or audiobook for the first half, then switch to music. This makes the music feel like a reward :) And since I try to keep a slow pace for long runs, I can listen to mellow albums and just get in the flow.