After submission there’s a nice opportunity to get a little feedback. Just a little, mind you, not too much.
You know what you know. You know what you think. You probably have some idea of what your supervisor thinks too. You know what others have said at conferences and in seminars and so on.
You don’t need a lot of new feedback at this stage. You have years of it. What you need is just a few thoughts to help you keep thinking in new ways about your research.
Ask for what you need. Ask your supervisor for their thoughts on your strengths, and if there’s anything you could have done differently. You’re not problem hunting, just exploring ideas. Tell friends about your research, and ask what questions they have. Offer to give a seminar if you have time, and listen to questions from that.
A little feedback can go a long way.