Real people gain skills and abilities by repetition and practice. Spending four hours a day hacking at a straw dummy with your sword for weeks on end is not exactly conducive to thrilling storytelling, though, so this part of an adventurer's life is usually glossed over or completely ignored within a game.

Some games have rules for covering the "down time" that occurs between adventures. In these periods the heroes can be assumed to be doing all the boring exercises they need to do in order to convert their worldly experience into actual skills. In some games you can even specify that X hours per day will be spent studying some skill you wouldn't normally otherwise learn about - either from books or a tutor - and once you rack up enough hours of study you can gain levels in that skill. So your swordswoman could learn to play piano on the side, if she really wanted to. You can do all this without the necessity of actually roleplaying 200 hours of piano lessons (although our GM here has a slightly different take on this idea - perhaps because of Pete).

This all assumes that you go to the effort of using such rules in your game. And that you don't keep throwing disruptive adventures at the heroes in rapid succession - which is another good way to prevent them abusing the system!

Transcript

Yoda: All in the mind, is the being of a Jedi.
Luke: Oh right. Nothing to do with swinging laser swords?
Yoda: Look at me. Judge me by my physical appearance, do you?
Luke: Only at first...
Yoda: Know why only Jedi use laser swords, hmmmm?
Luke: I don't know why anyone uses laser swords.
Yoda: A tool of defence, it is. Jedi use the Force to guide the blade.
Yoda: Properly done, it is impossible to hit yourself.
Luke: Whoa.
GM: Corey, add a point of Wisdom.
R2-D2: Wait. You're using the rule about spending time learning... and it improves your stats?
GM: We always have been.
R2-D2: Game. Changer. Okay, I'll draw up a schedule of strenuous tactical algorithm simulations. Which I'll just be doing all the time.
GM: But only if you roleplay it.