People say you have to have a lot of passion of what you are doing and it's toally true. The reason is because it's so hard. If you don't, any rational person would give up. It's really hard, and you have to do it over is to sustain a period of time. So if you don't love it, you don't have fun doing it, you don't really love it, you are gonna give up. That's what happens to most people actually.
If you really look at the ones ended up being "successful" in the eyes of society and the ones who didn't. Often time is the ones who are successful love what they do so they can persevere when it got really tough. And the one who didn't love it quit because you are saint. Who would wanna put up with this stuff if you don't love it.
So it's a lot of hard work and lot of worrying, constantly. If you don't love it, you are gonna fail. So you gotta love it, you gotta have passion.