I agree with ciretom.

First red flag warning here: the idea that the OP thinks things go bad because he's "nice."

Its' the classic "nice guy" rant. The reason why "nice" is in quotes, is because there's never been a "nice" person who was actually NICE. They are always people who worked out a list of "how to be nice," usually with an associated list of what they are "supposed to get in return for being nice" along side it.

Next red flag warning, that this is a repeating scenario. When someone does the same thing again, even though it failed, it means they are refusing to face reality.

Final red flag, the "I gave EVERYTHING" claim.

No. Actually, most people who think they "gave everything," usually never really gave anything at all. That is, they tried to give, but it wasn't what the other person wanted. When someone doesn't want what you are offering, then you haven't "given" them anything, you've just shoved things in their direction, and then patted yourself on the back for how wonderful YOU think you are.

I've been through an emotional grinder, as many have. And looking back, I know that from very early on, it was obvious to almost anyone except me, that I was blinding myself to the fact that she just didn't want what I was offering.

The thing to do, is to find the people who DO want who and what you are, and stop pushing yourself at people who don't.

What works sometimes is just don't be a pushover. It's great that people like you exist but more often than not...it goes unappreciated. Save it for later on in the relationship and just take it easy. Most people look at "too nice" as a weakness and or maybe insecure. That's my opinion anyways.