Yes, and it's a vicious cycle. For me the tension causes more blockage, causing more tension, etc.. This is why the oft-derided advice of slow down and take a breath helps me sometimes. At the very least it momentarily breaks that cycle, lets me clear my head, and reset. I think this may also be why I sometimes stutter less after a couple drinks. For me that loosens me up a little and makes me less likely to react badly when I feel a block coming on. I think everyone differs in their reaction to alcohol though.