Love the One You're With?

So an arbitrary dateline i created for myself was reached today. All i can think about is these lyrics from a song that was written way before my time.

Crosby, Stills, Nash & Young - Love The One You're With

There's a Rose
In a fisted Glove
And the eagle flies with the dove
And if you can't be with the one you love
It's alright
Go ahead and love the one, love the one, love the one your
with
Love the one, love the one, love the one your with
If your guy can't come to you
And you don't remember who your talking to
Your concentration slips away
Because your baby, she is so so far away
Chorus: And there's a rose in a fisted glove
And the eagle flies with the dove
And if you cant be with the one you love
Love the one your with
Don't be angry
Don't be sad
Don't sit cryin' for good times you had
There's a girl right next to you
And she's waiting for something to do
Chorus
Do it
Do it
Do it
Turn your heartache into joy
She's a girl and your a boy
Get together, make it tonight,
You ain't gonna need no more advice
Chorus
Just love the one your with

My problems with this... well almost all of it. Are you suppose to just settle? I mean, some people should (like ugly people) but are you really suppose to be unhappy and live some kind of lie? You're heart's not going to be in it. THAT'S IT! HA! Isn't that crazy, trying to love the one you're with when your hearts not in it is impossible. You can't 'love the one you're with' because you can't make yourself love someone if you don't. Then you're just hurting the person that you end up being with. Or...
My god, are they right? Should you just cut your losses and try to forget that amazing person and keep on dating the looser? I'd like to believe no. In the real world though, how often does that happen? Too often.
Third option: you don't get to be with the one you love, you tell the one you're with that you just don't feel it and you just go it alone. How depressing.