Sure! I question myself all the time. I've felt pretty low once or twice when I've done a bit too much over thinking and wondered if I truly am a waste of space. Then I remember that actually I have some strengths. I'm kind, loyal, caring and friendly (in real life). I remember, when I pause to think, that it's pretty unpleasant of people to call others thick, to judge them based on nothing but a political.opinion, to shout them down without really hearing them. I also remind myself that intelligence isn't really a concept well understood or necessarily something to be revered.
As it happens, as far as 'intelligence' goes, I was once a member of mensa! It got me a job I needed at the time, and then I left. I have an IQ of 155 which apparantly, as far as an objective measure of 'intelligence' is concerned means I'm not 'thick". However, 'intelligence isn't really to me, all about a number or a measure on some test. I have little confidence (perhaps if I am truly honest, that's a second reason I joined MENSA for a year, in addition to it helping me secure a job, I wanted to prove something to myself), I can be quite an anxious person, I clearly don't hold the mainstream view on some topics (brexit being the main one), I lack common sense and I am not always very assertive. So I do think in some ways I am thick.
I don't know if that's the answer you were after kendodd. If I am your definition of thick, then I guess I'm thick. Not sure how calling me that helps anything though.