Why is it so hard for a guy to admit that he messed up and apologize?

I know that it's not exclusive to men, but I do notice this more in men than in women.

You have to also understand that women are always right. Being right/wrong can be circumstantial as well as a matter of opinion. Personally, I won't apologize unless I know or believe I really am wrong. Maybe you should re-evaluation the circumstances from an objective point of view. Is he REALLY wrong or does he just have a different opinion?

Well, let's see. I sent him a text asking for advice on something, but I got no response. So I struggled with the problem for a couple more hours and still didn't get it resolved, so I called him, got his voice mail, and left a message. I still got no response. Finally, after a couple more hours, I got the answers I needed on my own. So I sent him another text letting him know. Then, a couple of hours later, he called and said something that made it clear that he had never bothered to check his texts or voice mail. I can't begin to tell you how frustrating it was to try to communicate with him and have him not answer or check his messages. So you tell me, did I have reason to be a little upset or not?

I would say that if he DID in fact inform you first, you shouldn't have expected it. You need to find a better method of communicating in case of emergency. Perhaps try email. I personally don't use voice mail and can't stand getting voice mail when I call someone. I may or may not read a text. If I do, I may or may not respond depending on importance. Likewise, I don't answer unknown numbers.
I do understand your frustration; but you partially brought it on yourself. Again, sit down with the other (whatever your relationship is) and come up with a positive solution.

Well, I agree that we do need to come to a better understanding about how we're going to handle situations like this in the future, but I still don't see how I could have brought this on myself. By the way, he's even less likely to check his email than his texts. As far as I know, he only checks his email once a day at most (after he gets home).

Agree to not call unless it's dire. In which case he should call you back upon seeing your number(S) in the call history.

That may be the answer. I'll have to talk to him about that and hopefully we can come to a mutual understanding.

Good luck!

Thanks!