Is it just bitter when there's no sweet?

If you think I need you,
You're wrong.

*I'd change this to 'you thought wrong"*

If you think I want you,
For a while I do.

*I'd change "do" to "did" that seems to sound better to me*

If you think you're my world,
Without you babe my world keeps on spinning

*I didn't like how you worded this. It threw off the flow of the poem. I'd fine some way to say that line just in a shorter line*

When you mess this up,
I won't miss your concstant sinning.

*Should "concstant" be "constant" ?*

If you want to stay,
I'll forgive you.

But don't blame me,
The next time you fall,
and I don't pick you up.

*I'd say "when I'm not there to pick you up*

How will you learn,
anything at all?

*This part seems infinished. I would add "If I keep picking you up, and making you whole again" I'm not sure if you were trying to rhyme, but the way you did it made this stanza a little awkward for me*

I will tell you that I love you.
This is not a lie.
But when you up and leave,
Don't expect a sweet goodbye.
You're not worth enough to worry about.
So when you fail me,
Like we know you will,
Don't cry when I say so long.
You saw it coming.
Like you've constantly told me:
"You're strong."

*This stanza was flawless. You put your emotions here and they weren't confusing or unclear. Nice*

So stay a little while.
Maybe we can make a memory or two.
But when the day you leave me comes,
I'm not coming after you.

*I like this ending. I think you did okay with this. The ending seemed alot stronger to me than the beginning did. I'd work on trying to balance it out so both parts are stong. I felt you wrote about something that is common with a lot of people, but you made it special to you and your situation. Not my favorite from you. I think you can do better. Keep working though. Nik*