From experience playing with people of all skill levels, here's what people who shoot triple digit scores do on a regular basis and how what they do can be quantified:
1. From the tee box: 2-3 balls OB or into unplayable (woods and lose ball) situations. Cost to round 4-6 strokes.
2. From the fairway: 2-3 balls into hazards or other unplayable situations. Cost to round 4-6 strokes.
3. Mishit 2-4 chip shots short or over green. Cost to round 2-4 strokes.
4. Miss 4-6 putts inside 5 feet. Cost to round 4-6 strokes
Add up just these simple errors and it costs a 100+ shooter 14 strokes a round MINIMUM
Help with these errors
1a. If you have water, OB or other hazard from the tee box, move as close to the trouble side as the tee markers allow and hit AWAY from the trouble area. Laying 2 in the rough is a real stroke saver over rehitting 3 from the tee!
2b. Same thing, look at what a fairway shot has to offer and layup short of a hazard, play AWAY from the hazard or simply play a shot with a club that you have the most confidence in even if it means playing a 7-iron as a second shot on a par-5.
3b. Practice your short game (pitching and chipping) wherever and whenever you can. Practice goal for a 100 shooter might be getting those greenside pitch and chips up and down in THREE shots instead of 4 or 5.
4b. Same thing with putting. The best way to reduce missing the short makeable putts is practice, practice and more practice. Before each round, I take 2 balls and make both balls from all 4 sides of the hole from 2, 3, and 5' range. One stat I always look at after each round is how many 'makeable' putts did I miss? It's usually 1 or 2 at worst for an 18-hole round.
Finally, lets say you can correct these errors at an 80% success rate by playing smarter and some practice. The 14 shots of errors are correctable at a rate of 11 shots per round. Your typical 106 round is now a 95.
My biggest concern when playing is to eliminate all unforced (self-inflicted) errors in a round. This is pretty much the only way I can keep the scores in the mid- to high-80s anymore. It works for me. It can work for you.