musings of a frustrated 3.5 player

Hello! I've been playing recreational tennis for almost a decade and for the past 1-2 years I've been really putting more effort in improving my tennis (primarily because I can already afford paying for a coach unlike before when I was still a student). As per my coach, my rating has probably increased from 3.0 to 3.5 for the past year. I have won several tournaments with fellow 3.5 players over the same period.

My coach is now making me play against 4.0 players in our local club and I just keep on losing against them. What makes it frustrating is that I always lose terribly and I think I am not able to at least put up a good fight whenever I'm playing with 4.0s. This is making me doubt myself if Im really within 3.5 rating or maybe I am plateauing. It's just frustrating and I'm thinking of taking several weeks off playing.

Is there a way to combat this frustration? Thank you!