How do i detach

I've been with someone for the past 10 months and i used to be so in love with him and all , but for the past like 3 months , its been rought , he stated showing his truth , and he's a manipulative gaslighting peace of shit , but i didnt find out till i was deep in love , and i kknow that this may be kind ve weird but for some reason ive always been a leave him type of a friend but now that it happened to me for some reason i just can't stand on business and leave , i think im scared of being alone after , and i also dont want to let go of the person i knew in the beginning, it gives so much anxiety and even tho ik what i should do , i cant seem to do it , so is there any way i can just detach ? I cant keep doing this .