Focus, if you want to be successful.
This is what society always tells us. But creative people, don't find that very appealing. We always want to do a bit of this, a bit of that, and a ton of other fun things. You may be thinking, “If I stop doing all of this and focus on one thing, I will stop learning and developing.” This is not entirely true. Firstly, focusing doesn't mean that you do one thing all the time. You can still do other things you like in spare time, so you don't need to stop doing them. Secondly, you will not stop learning because... read the previous sentence. And there probably is a lot to learn in the area that you chose to focus on. Nevertheless, setting an area of focus is a limit that will slow you down in other areas while giving you a huge boost in the chosen sphere (and that's the whole point of focusing).
Do you want to be a master?
Another thing that always scared me about focusing on one thing is becoming a master of something. It was because apparently I confused mastery and craftsmanship. I always thought that being a master means being the best at one thing. And I imagined this thing to be something simple (not easy though) like making pots. Always making similar pots looks boring to me. But if you draw one thousand pictures, make ten thousand different pots or build a hundred startups, and if you love doing that — I doubt that your life will be boring.
Mastery ≠ Craftsmanship
Although you could choose one style for your pictures, every one of them will be different and the style will be evolving, so one day you could take it to the next level and become a true master of painting. Same goes for pots. And for startups: I doubt that every startup you build will be the same. You can't be a craftsman of startups, but you can certainly master this area if you focus on it.