You might actually be too legit to crit, because you might have rolled something different and just said you did. Thing is, nobody likes to lose. Losing is not enjoyable. You do not progress that way, and you die… rather, your PC does. The one you worked hours (or days) to create. It’s a bad situation for a gamer. It’s hard to always roll it behind your hand without others noticing, or rolling as if you “weren’t” and then pretending that last number was what you just rolled…
I used to roll lower on the die than what I said. I didn’t like to lose, and I often rolled badly anyhow. But really, how can a gamer roll “badly” when it’s gravity (or chance) that determines where and how the die will ultimately land? Well, that’s when you, as a real gamer, must learn acceptance.
Yup, that’s the key: acceptance. (For that matter, this helps in life, too.)
Because I learned the value of gaming truthfully, I have had no “reason” to fudge my rolls. There’s not much point to always winning, is there? (Except winning, but stay with me here…) The nature of rolling dice is chance. Without the capability to fail, there is no chance to win. So, the moral of the story is: give your DM a break and stop being mean about your rolls. The world will not end if you botch; often, it becomes more interesting.
(This also goes for skill point allotment and the equipment you started with for the campaign.)