Too many times...
You are uncertain which club to hit into the green. You pick the shorter club knowing that you have hit it that far before. You remember that one time you hit your 8 iron 150 yards. You forgot how you hit it perfect, straight, downhill, downwind, and it rolled to the center when it bounced on the front collar. This time it falls short into the front sand bunker.
Most amateurs try to hit their perfect shot every time and wind up short. The better option would be to take the longer club, swing easy and end up on the green or on the fringe over the green. Very few amateurs hit over the greens.
Take an extra club on every shot for 18 holes. When you are finished with your round, count how many times you were over the green. Chances are, not many.
If you are 150 out, and your max 7 iron is 160, then use that club knowing you can easily carry it 140-150 with a smooth swing. Your 8 iron max is 150, but you average 135...meaning, half the time you won't even make it to the front of the green at 135. Not to mention, course designers protect the front of the green more than the back.
Into the wind, take two more than normal. If the pin is at 150, but you are into the wind forcing you to play it like it was 165, then take one additional club for wind, and another to swing smooth. The last thing you want to do is swing hard into the wind because the wind exaggerates the spin. It can cause the ball to balloon up, and then come straight down short, or it can over-exaggerate side spin, too, causing your slice to turn harder, now right and short.