Your in the same boat as every honest hunter who has hunted for awhile it happens.You may of gotten a little buck fever with out knowing it.This also happens to alot of veteran hunters but alot of them won't admit it.Next time take a couple of deep breaths and talk yourself into the shot on what to do and where to aim.You would be surprised how many hunters when excited never really aimed at the deer only quickly pointed at it.
You have more time then you think.