I try to make it a routine to "stretch" myself musically. Sometimes it is just playing a piece that I have known for years but trying to do it in a different timing, or perhaps adding some different notes here & there.
Also, trying different styles of music outside my usual helps. I learned a bit of classical doing this & have incorporated it into my usual styles.
Right now, I am writing a "blues" tune, doing a melodic run on the bass strings while doing another melody on the high. I hope to eventually get it "smooth". Also, I am hoping to blend this "blues" bit with a few classical strokes.
Stretching is like walking. The only way to progress is by taking another step.