I would like to offer a few things here if you dont mind
1. Make sure you get a firm knowledge of the basics, things like center line, grips, where you weight is compared to thiers, leverage and your position being relative to your goal ie...if you are want to sweep, where are your hips and where should they be to execute that sweep.
2. Dont focus on not getting submitted when starting, this is the time where you will learn and learn from your mistakes. Also if you are rolling with someone more advanced, ask questions like what could I have done different in that situation, what did I do wrong, what should I have been aware of that I was not....do not be afraid to ask questions and learn from them.
3. Most important is to have fun, if you are not having fun, you will find yourself bored or losing interest.
4. Get alot of mat time in, Rome was not built in a day and your game wont be either, takes a lot of time dedication to become at anything, BJJ is not different