The ability to focus in on your core competencies is a major asset. We all have multiple talents, commitments and activities. Some create a lot of value, while others do not. The goal (particularly on the business side of things) is to determine which activities create the most value and focus resources on those. Value could be happiness, money, whatever it means to you.
So Drew, to answer your question, YES, drop things that you have gotten out of practice with and aren’t truly passionate about anymore, even if they are making money. I recently left my web design business of 7 years that generated great revenue for a college kid to instead focus on a new tech start-up that statistics and probability say will fail.
Never sit still. Take the risk, go for the gold. Don’t get caught up in the little wins, it’s the big ones that actually make an impact. Always consider, what is the worst case scenario? Maybe some lost time, lost money, so what? Think about the opportunities that have a time window – if the clock is ticking, grab them while you have the chance.