Snail on my sleeve

Disclaimer: Before anyone thinks I'm talking about them, don't worry; I'm not. It's all about me. Me me me. XD

So, I have a problem.
This problem has been around since I've been born:

I wear my heart on my sleeve and I easily fall in love.

I do. It's all or nothing for me. I either care about someone/something or I don't. And if I'm inbetween, it's just because I haven't made up my mind yet.
And I don't just mean with people; I mean with animals and inanimate objects.

Example:
There was a snail on the side of my apartment the other day. I cooed at it and waved as I went to work, thinking that snails are slow and I'll see it when I'm on my lunch break.
When I came back on my lunch break, I found it crushed. It had worked its way to the ground and had been stepped on.
I was so sad.

Is this normal?

And this leads to even more problems than crying over crushed molluscans; it leads to me getting in my own way.

If I'm giving 110 percent, for some silly reason, I expect it in return. Be it friendship/relationship/coworker....ship.
Then, when the 110 percent isn't given back, I'm incredibly disappointed.
I set myself up for the fall!

Why?!
Why do I continue to do this to myself?!
Why do I think that someone is going to be on the exact wavelength?

It's not really purposeful..... it's pretty much automatic with me.