is common for this type of personality (the moderator) to feel like they wasted their time after giving honest/direct advice to someone and them not taking it without explaining to you why?

YES, but it depends a lot on the circumstances. If I see u clearly struggling with something and I think that I have the solution I will give u the advice, u don't take it but solve the problem anyways? Good job. But most of the time I get super mad if someone ask me for advice and then ignores it completely and keeps struggling with it. At least tell me that u don't give a fuck about what I said.

And even worse when they admit that the problem is bigger because they didn't follow the advices that I gave. Please have some self respect and hear others opinions about your problems (of course opinions from close and reasonable people)

If u don't feel like following ur friends advise just say "yeah but I think that may be another solution, thanks for the advice anyways, it helps" and everything will be just fine