Trained delts and triceps: Used one set to failure.
Press behind the neck. Warmed up with 115 then 125lbs. Then my shoulder screamed. Nope not doing that again. They use to be a favorite of mine.
It's annoying when people give advices (because we know it all since we've been training for 40 years!) but here's my 2 cents.
Regarding bench pressing and behind neck presses (or any movement you that you have trouble with from previous injury).
Start really light. Just the bar or no weight on a machine.
Do your 8-10 reps or whatever.
Add weight VERY gradually over several weeks and months to allow your muscles and connective tissues to strengthen and gain flexibility. Add only a few pounds at a time.
Example:
Week 1 and 2 - Empty bar
Week 3 and 4 - Empty bar + 2.5 to 5 lbs.
Week 5 and 6 - Empty bar + 5 to 10 lbs
Etc.
Warm up gradually. Add weight during warmup sets in jumps of no more than 10% of your max. If your max is 250 in the squat then add weight each warmup set no more than 25 lbs. Even less if needed. Yes, you will need to do more warmup sets.
The introduction of a new movement to a routine requires a period of adaptation to prevent injury. When you get older this seems to be even more important. If you haven't done behind neck presses in a year, start very light.
My elbow problem resulted from doing an exercise I hadn't done in years using heavy weight. Result: injury! The connective tissue couldn't handle it. What I should have done is used light weight for a week or two before going heavier. Dumb!
Regarding diet and exercise in general...
It's easier to skip the second helping of fried chicken or the second beer than have to spend an hour or two on the treadmill walking it off. You can still spend an hour on the treadmill if you want to (because you just really
love the treadmill or you are addicted to the endorphin rush) and then you'll lose weight if that's your goal. Or you could rest, recover and read a book. Growth only occurs during rest right?
Excessive exercise doesn't significantly increase your life span. It can improve your quality of life (as long as you enjoy exercising) but you have to weigh that against the time you spend exercising that you could be doing other things you may also enjoy. If you love exercising then do that.