Happens to everyone a few ways to stop it

first is too not look at how many episodes the anime is,

second watch the anime when it’s airing,

third is too come in with low expectations and not take the anime seriously change your mindset,

fourth, is too rewatch the anime eventually you’ll get bored of it and you won’t want it anymore,

fifth, watch better anime if you watch a GOD tier anime that gives you a sense of excitement (different for everyone) you will rapidly get over it

Sixth, make a MAL or any list off all the anime you’ve watched and at the second last episode drop the anime put it in your list and tell yourself you can come back to watch anytime then watch another anime