Step 1: Know who you are
This is the most simple but for some people the hardest but a very important factor. There is honestly nothing more frustrating than coming across an artist who doesn't know who they are. You need to be authentic, people can see through it when you're trying to be someone else. Even so, there's no fun in being someone else because that someone else already exists. You'll always be second place to who they are so it's important to stick to who you are and do you better than anyone else can.
Step 2: Know your audience
Not everyone is going to like you and you need to accept that, so you need to find people that are going to like and support you. This is an important factor in having a sustainable career as a musician. Don't try the scatter-gun approach, it sometimes works but in the long run it is not sustainable. The trick to finding people to like you is by knowing yourself, so go back to step 1. The people that will like your music will also like what you like.
Step 3: Connect Step 1 & 2
This step is vital in sustaining your career. You can't have one without the other. You could be the best musician who knows who they are and makes the best music, but if you aren't connecting with your audience you cannot sustain a career. It's okay to be a musician who just makes music for yourself or your friends, it can be form of therapy or entertainment but if you want to have a career in the industry and you want to make MONEY, you need to make sure you connect you who are to your audience. Most true musicians make that mistake.