And when you've grown bored of your new plaything, you'll come back, like you always do. And I'll be here waiting, like I always am.

You've probably heard this a hundred times ...but , please don't do this you are just making yourself available for someone who doesn't care about you.
Whoever this person is they only care about themselves.
Hard truth I guess but I hope you can find the strength not to let people do this to you