You fall for the love bombing, then think you must have done something wrong when it stops and the mask starts to slip. You blame yourself because of poor self esteem or behaviour patterns you saw when growing up, you're desperate for things to go back to the nice way they were at the beginning.
Your boundaries were probably tested early on, but maybe you didn't notice because it was under the guise of him pretending to be upset or hurt by something you did, so you told yourself you mustn't upset him again. Or you tried to stand up for yourself but were made to feel stupid and like you'd got the wrong end of the stick. Either way, your boundaries get trampled and you stop standing up for yourself without realising.
Every time you feel shit or distressed, you think you must be over sensitive or you (personally) aren't very good in relationships and it's really you that's the problem.
He makes you feel like you're being difficult/crazy/insecure/argumentative for questioning anything or trying to explain that something is an issue or you felt hurt.
He shuts down any attempts at communication and makes you feel awful for trying, so you give up and accept things the way they are.
You feel overwhelmed and alone, but even though you feel terrible, you ignore your gut instinct because you don't even think you can trust it now your self esteem is so low.
You think he's not so bad really, no one is perfect, you're a difficult person yourself, at least he doesn't.......until he does and you crack under that final straw and that's when it ends.
This might sound familiar to other posters and is basically a summary of 8 years of my life up until I filed for divorce.