From my recollection, Hagler always denied the cocaine use, but accepted he might have been on the pop a bit more than usual. There had been marital disharmony, at the time, which ended in divorce. Nothing out of the ordinary, in the scheme of things and, whatever was going on, it doesn't look like it ever spiraled out of control.
Especially in light of, per his own admission, he was barely literate in his 20s; while he grew up poor like many fighters, he had the sense not to blow it all to compensate for that kind of past. He saw what was happening to Ali in training camp, surrounded by con men and hustlers ready and willing to take full advantage of easy money in the guise of friendship, and made sure he didn't make the same mistake. Couple that with a scandal-free life (really respect he's still married to the same woman who saw him through it all), and you have the marking of a well-lived life.
As Holmes put it, "I have a PHD in common sense." Unfortunately a lot of boxers don't. They squander millions on cars, mansions, yachts, planes and all the rest (but don't bother to pay any taxes or child support for their 11 kids) and wonder why they're broke when they retire.
Honestly dont know what else you want me to say except again things look like they couldnt be better for him. Seems like a great guy
Sadly I could not include Tunney on the list. His life was touched by tragedy, and he drank himself to death.