Geez, there are so many where do I start.
Shooting at an antelope off a bipod at long range but only one leg of the bipod was on the ground tried to hold the other in my hand to get the scope level, at the shot the bellet was thrown to the side held in my hand, missed by 3 feet.

Got lazy and left my pack with extra bullets at a trail fork, cause I had not seen a deer in 3 days and did not expect to see one and I had to climb up quite a ways.
Sure enough I jumped a big buck right on the trail he ran through the trees and stopped at 250 yards, normally I would have used my pack for a rest and I would have gotten than buck, there was no natural rest available so took three bad shots (you know the kind of shots you take when you don' t have a good rest and you are huffing and puffing from running to get into position) as he was moving through the trees from the elbows on the knees. I saw him again 20 minutes later at about 400 yards just before dark but only had one bullet left so chose not to attempt the shot.

Can' t tell you how many running elk I have missed in the timber at less than 100 yards because I stop the rifle when I shoot instead of following through and shoot behind them. I know I do it but in the heat of the moment I can' t help it.

My all time worst was bowhunting, I had a nice five point bull at wallow 1 hour into my first ever bowhunt. I was sitting out in a meadow behind 5 scrub pines.
I drew my bow back and then had to turn a little to shoot him at 20 yards. Just before I got in position the arrow hit a small branch on one of the trees. Now I am sitting with my sights on this bull but my arrow is resting on my elbow.
So I start trying to bump it back onto the rest, 3, 4, 5 times, nope not gonna work. By now the bull is staring at me and by the 5th try he is out of there. Thought my heart was going to pound out of my chest. Bowhunting is great!

Anybody else?