> However empirically I found that the more convinced one is that they don't need advice the more badly they actually need it.
Empirically, I found the opposite. ;-)
> Objectively, if I was deciding on whether I want to be married or not
You decide that subjectively, not objectively. It's actually pretty simple: be single for a while, and see how it feels. If it sucks, then try not to be single. If it's great, then continue.
There's also the crucial matter of marriage being a mutual decision between two people, so one can't just decide to get married. I will offer some advice myself though FWIW: if you're not in love with someone, or they're not in love with you, then you probably shouldn't marry them.