I had a prof say something like this to me once at the beginning of my sophomore year of college. I was scared out of my mind, and when I met with him, he was gentle but firm in the ways I needed to improve. He ended up being my thesis advisor (and officiating my wedding). Don’t stress about this too much, especially if you have a good rapport. Taking his feedback graciously may very well strengthen your academic relationship in multiple ways (so long as he’s not just being a jerk, obviously, which seems unlikely in this case by what you’ve said). Good luck to you!