Pretty much all the time, yeah. I don't know if it's a mild Impostor Syndrome (which is quite common for creative types), but I walk around thinking "Well, sooner or later they'll figure out I'm making stuff up as I go along", and I am forever questioning myself. But I do my best to not let it get in my way.
One of those things is that I do my very best not to compare myself with other artists, which is a difficult thing to pull off sometimes. I try to make sure I only compare myself with myself. Like, I'm a better artist today than I was a year ago - and I was a better artist a year ago than I was two years ago. I can only ever improve myself, so that's the only person I should be comparing myself to.
Look to others for advice and inspiration, but look to yourself for someone to compete against.