See, the thing is; actual nice guys don't have to constantly convince everyone around them that they're nice; because if they're actually good people, it's obvious. If someone is truly a good person, there really shouldn't be any cause for a constant stream of reassurances that they're the best, and anyone who is able to witness their graciousness should be grateful. Because, at the end of the day there is a really big difference between being confident in your authentic self, and portraying yourself as a great person to everyone you meet for your own benefit.
Maybe I'm jaded from personal experiences, but I truly believe that as soon as someone (especially men, sorry guys!) tells you in more ways than one that they're really a nice person, and you know, it really is their ex's loss anyway; it's time to book it. It's easier said than done, and maybe it sounds crazy, but hear me out.
Why would someone with a kind heart who only wants the best for you, constantly be trying to convince you that they're the best person you'll ever meet? If you want my opinion based on experience, it's because they know as soon as they start showing the less attractive or more cold side of themselves, they can say "remember, I'm a good person." Another aspect of it is that you'll always have that underlying subliminal message going through your brain because they never stop talking about how great they are. Really though, I think people who boast about how wonderful they are to others, are really just trying to convince themselves that they're better people than they know they actually are.
A person constantly telling everyone around themselves that they're great will start to believe it as long as no one tells them otherwise. The thing about people who think they're perfect is that they usually only want to have people around that agree with them, at least to their face. On top of the fact that a lot of men can't or refuse to see their own flaws, there's another side of it that bothers me. The reason this kind of behavior aggravates me so much is because by doing so you're assuming that I'm too stupid or weak to see through your lies and deceit. What makes a guy think that just because he says he's nice, he can get treated the way a genuinely good guy would?
So, all in all, my advice is to try and stay away from people who only brag about being good people, instead of actually being a good person. Because they shouldn't have to say it, it should just show naturally. And, it's easier said than done because the kind of person that does this makes it hard to see past the good things they've done, over all of the negative aspects that they bring into your life. But, I have to say, it is kind of fun telling people that they're not as great as they tell everyone they are. I mean, someone has to do it eventually.