Unfortunately most of the time they are in denial and feel their
actions are justified by "others making him that way". It will be
even harder to try and talk to this person about it because that
may set them off as well. It may be an idea to have someone that is
very close and trusted that agrees you to speak to this person. But
please do not feel you have to put up with this behaviour - most of
the time it gets worse not better.
If he also drinks or does drugs, you could help save his life by
getting him to go to Alcoholics Anonymous or a drug rehab. The
symptoms you describe match those of most alcoholics. He can be
very capable and still be an alcoholic, he does not need to be
sleeping under a bridge to be an alcoholic. Alcoholism is not a
moral problem, it is a physiologic allergic reaction some people
have to alcohol that others do not. Just like some people are
allergic to certain foods like shell fish while others are not.
Once an alcoholic gets the first drink into their system, the
allergic reaction is often triggered and they want to drink more.
Eventually they drink until their judgment is impaired and they do
things they normally would not do otherwise. If the Pope or Billy
Graham drank as much as the triggered alcoholic does, then they too
would loose their judgment and do things that went against their
own value system. If a person is an alcoholic and just stops
drinking without getting full recovery, they are called a dry drunk
who is miserable inside and therefore restless, irritable and
discontent; and make everyone around them suffer too. Bes tbet is
to get them into recovery, or get the out of your life.