To paraphrase the saying, a jack of all trades is a master at none. Why is that? If you spend your time doing a hundred different things, you’ll be fairly decent at all of them, but never a master at any of them.
For example, I read about a world-class chess player (can’t remember his name and it’s not Kasparov), who had only one interest, chess. He said that he was so crazy about chess that he spent nearly every waking second thinking of it. In fact, it was so bad that his mother wanted to take him to a mental hospital (apparently she didn’t). The point is, he is a genius chess player because he spent all his time improving one skill.
So now the question is if we should do the same. Pick something you want to be a master at and obsess over it and spend no time on anything else. Personally, I think that might be a bit overboard, but the fact of the matter is that you will be better at something the more time you spend at working with it.
Therefore, if you follow me so far, choose your battles. Limit your choices and make sure that every minute you spend is spent the way you want. I’ve often seen people saying that writers should stop watching TV. I happen to like TV and movies, so I wouldn’t cut it out. You have to ask yourself, is this thing worth my time? Do I really want to spend time on this? (Just remember to give yourself some off-time.)
Pick what you want to get great at and do it. All the time. Then a master you will become.