Getting into the music business is hard enough, selling records and staying successful is another matter altogether. There is a reality check that you have to face at some point in your career as a musician; this could be before you start, in the middle and sadly towards the end. The hard truth you have to face is – accepting what you are good at and giving people what they want.
For example, you may be a singer/songwriter who loves to sing. But if you come to realize that your writing is way better than your singing, then you have to give up the singing and put all your efforts into writing songs. Being successful also means being prudent. A great example of this is the artist Babyface; he had a decent singing career, but his songwriting and producing capabilities were far superior to his singing. So he ended up focusing more on that aspect which has brought him tremendous success in that field. This is one aspect of figuring things out.
The other aspect is accepting who you want to play to. You could be great at playing a fusion of country western-snake charmer-Australian aboriginal music, but you could be effectively playing to an audience of one. Sometimes your passion has to take a backseat to building a realistic career. You do not necessarily have to turn into a boy band or girlie band and churn out sticky nonsensical hits, but you will have to change to fit a more commercial style if you want success on a large scale.
Figuring out these things early in your career will help you to map out where you want to go and what you want to do. Reality is also a bitter pill to swallow.