Ponder the song you're working on. What is its essence, what makes it important, special? It's really sad, or jams, or uses amazing range or speed. Whatever defines it, think about how to make it even more so. There will be musical AND psychological, attitudinal elements to this - for example, a song that's core principle is sincerity, earnestness will usually have a simple chord structure, not a lot of licks in the melody or a busy bass line, etc. In working on this song, you should think about it both ways - Psychologically first and what are the implications of that (Song is sad so how can I create that even better? I'll put lots of dynamic contrast in, lots of connection between notes - but letting the idea of sadness lead). And then Technically - this song is fast and technically amazing - I guess it's sort of Jammin' and up-in-my-face. I'll think about playing like that. Use the psychological synopsis of the song to give you inform your playing.
There are several million good songs. Only learn great, important, and special ones, pieces you love.