Obviously, given the venue, spending more time on your bike is recommended. Then cast around a bit for another game of some sort that you enjoy. The fishing is reported to be fantastic in Costa Rica. Not sure about the options for golf, tennis, etc. Sailing perhaps? It all depends on personality and what you like, but you might give serious thought to trying out some computer games, they can be fun and quite adictive. If you have a LOT of time on your hands I would recommend Everquest, you can fiddle with that 24/7 for five years and still have stuff that needs doing.
If not of that works you may have to break down and start up a new "retirement" business.