This depends. Is it someone I'm obsessed with in a good way, or a bad way? Two different approaches.

If it's someone I can't stop thinking about because I'm in love with them, I don't see a problem. If it's someone I can't stop thinking about because they've done something that upsets me, I try to distract myself. I pet my cats, harass my bunnies by forcing them to let me pick them up, or stroke my lizard. (No, that's not a euphemism.)

Unless you’re fortunate enough to fall in love again, I’m not sure it’s possible. You can only let time help the memories fade.

I've yet to figure that one out.

Brain surgery

Not easy

Write about them

You just do it.

WD-40

Mix 500ml of water with 2 table spoons of pink himalayan salt, 10 ml of apple cider vinegar and 5 ml of bleach. Put it in a gravy boat, put your head under a sink and pour the mixture into your ear.

Every time you think of them remember something awful about them then think of other things.

Sleep with someone else

Mix 500ml of water with 2 table spoons of pink himalayan salt, 10 ml of apple cider vinegar and 5 ml of bleach. Put it in a gravy boat, put your head under a sink and pour the mixture into your ear.

Learn to empty your head with meditation, or fill it with something else.

Another lobotomy.

Fill your head with other things.

Figure out why they are in there in the first place and deal with the source

Replace with something of equal or greater power.

Enough liquor or a full frontal lobotomy

00000000 <-- this is an 8 bit set, if read right to left, first place is 1, next is 2, next is 4, next is 8, next is 16, next is 32, next is 64, next is 128. If 1, it's ON, if 0, it's OFF. Now Sum.

(binary) 00000101 = 5 (decimal)
(binary) 10000001 = 129 (decimal)


once you learn this, use as needed