I used to believe it got worse under certain circumstances like if I was tired or hadn't slept or maybe under stress but I've been in those situations many a time and it usually either makes my stutter worse or makes it better. I've worked in a call center taking emergency calls and my stutter was manageable until the end but I did have bad days here and there. In my last month there, my stutter became much worse and I had a horrible last month there and I have no idea why. There have been times where I haven't slept or been very tired and the same thing happens. My stutter will either become much worse for a moment or vanish. Idk about the last. I'm not an overly confident person but I do try. I've been told a lot that I have no self confidence.