Make decisions when you are ready, not under pressure. Others will always push you to make a decision for their own purposes, internal politics, or some other external need. But you can almost always say, “I need a little more time to think about this. I’ll get back to you.” This tactic is very effective at defusing even the most difficult and uncomfortable situations.
You should be doing something that you're passionate about and that you think is really important.
The pursuit of mathematical knowledge is a never-ending adventure, filled with challenges, surprises, and the satisfaction of solving the unsolvable.