Marriage is like 2 different personalities trying to make a relationship work. No matter who you choose, there's bound to be differences.
During courtship, there's rubbing and friction. You get to discover shocking facts about your partner and your partner also discovers that of you.
What I encounter is, when both of you are planning for marriage, you have more fights. Worse fights esp if there's pressure from parents.
Different people have different expectations of their partner. Different girls look for different things in a guy. If you want a guy who can lavish upon you gifts and bring you to expensive places, he may do it now cos he could afford but do you know if he's forever well to do? Even then, his heart may be cold towards you ater both of you are married for years. Of cos not all rich men are like that.
What I mean is, what does your partner chose you for? If he's with you bcos of your looks, he will do so if he fancies someone else or when you're getting older. I've seen married women who exercised themselves mad everyday and do all sorts of things to their face and body to keep their husbands when their husbands are fat like pig and old. There are also newly wed wives who exercised incessantly and diet constantly when they're all bones. It's sad.
Altho people may change, I believe characteristics don't change much. How he treats people around him, his colleagues, his subordinates, his parents, his siblings ... he may also treat you when both of you are older. Why not? When he hasn't gotten you, he'll do all sorts of things. But when the love is old, he will treat you like the rest.
Honesty is important. Of cos, both of you definitely have some secrets of your own but if important issues like finances or his family, he has problems sharing or opening up to you, chances are he will be 10 times or even 100 times worse after marriage.
Men don't change. Girls also don't. They only change if they do it for themselves, if they want to, or else it's temporal. It's fake.
When you are dating, when in a relationship, open your eyes WIDE bcos after marrige, you can't choose anymore. The tell tale signs are there. What you see is what you get.