Letting go?

So I’ve had an on and off thing with this guy whom my friends and I refer to as jaguar (yes it’s a code name😂) . He’s extremely toxic and I know it but every time he leaves I let him come back. Sis I know this is dumb but I can’t seem to shake him off. No matter how hard I try I constantly let him back in. There’s just something about him, and I know he’s only in it for the sex (he said he’s not) .I tried talking to him but he just said we’re never going to be together. So I decided to move on and it’s been couple days later and I’m doing fine. Except now jaguar is texting me again. How do I let go for good? I swear letting go of someone you truly like is the hardest thing ever!!!