1.) The agent hates me. Unless you approached her and said something along the lines of, “You and your kids are ugly and you have lousy taste in manuscripts,” a rejection shouldn’t be personal.
But if you are worried that you unintentionally offended an agent or other publishing professional, take action. Email to let him know you have been worried about why you may have been the cause of offense, followed by an apology. Chances are good the other person had no idea he should have been offended, and has been enjoying the beach, not thinking a thing about the “incident” that has you worried. Or, if he really was offended, he should accept your apology. Then you can make a fresh start.
2.) The agent was making up an excuse to reject me. Except when writing blog posts, we don’t have time to wax long and poetic. But if an agent says anything beyond a catchphrase such as, “This work is not a good fit for me,” then I would consider the advice. Those phrases might include allusions to the quality of writing, slim market for your type of work, or other hints as to why your work was rejected. This hint could help you learn what might work better for you in the future.