is that a myth or is it true because i swear sometimes i feel that when i shave off my beard and grow it back out for a few days, it looks thicker and darker. maybe im just going crazy
I don't think so, either. And I actually enjoy having a day or two of growth. For whatever reason, I get a better shave when there's more to take off.
Now, I'm not saying that Snopes is the most reliable source in the whole world, but they seem to do their research and back it up with expert opinions. A quick google brought up this: http://www.snopes.com/oldwives/hairgrow.asp
I like when they say that if the claim were true then bald men would be cutting/shaving their hair (or lack thereof) constantly.