It depends on the negative feedback. Sometimes we can’t please everyone and not all personality differences can be resolve. There will always be someone who has something negative to say about us (especially if we are teaching classes/groups). If this is happening frequently then you need to take a step back and see if there is anything you can do to fix the “issues”. If it’s one or two people who gave you a negative feedback then worrying about it too much won’t help you or make that much of a difference. You can always confront those who gave you the negative feedback and see if you can do anything to resolve it. Or you can talk to your manager/fitness director and maybe he/she can give you a helpful advice.