I'm not sure what to make of this situation.
Over the years, my manager and I have developed a personal relationship at work. Aside from the regular communication of responsibilities, we joke with each other (and the rest of the team), talk about our lives, families, and other stuff.
Thinking back at my previous year at work, I sometimes notice a look of discontent on my boss's face whenever I describe my solution to a given problem (happened once or twice). For the first couple of times, I asked if anything is wrong, and all I got was a "no, no, just keep going at it". Even if you look at my performance reviews, you can see that there are no criticisms there. And no, I highly doubt that this is the case of the oft cited Impostor Syndrome, because I'm often very well aware of what I can improve in my work. Not to mention that I feel that this might be an impediment to me improving at what I do, which is ultimately the most important part of my work experience.
Because of this, I've become a little bit uneasy. I worry that our "closeness" (if you will) is getting in the way of him criticizing my work, even though I have repeatedly stated that I welcome this. I keep thinking to myself that next time will be the last straw, and that I will be fired out of the blue. Needless to say, I don't want this to happen, and I would like to honestly discuss this with my boss without being unnecessarily confrontational.
So, my question is: should I resign? And if not, is there a way for me to bring it up with my boss in a professional way?