when i fp someone its pretty obvious. i dont really keep it in. il even just tell them. its a burden on them if they are unattainable or find me irritating, so the faster i can decouple myself from them the better. however, if for some reason they didn't know, i guess i would just try to self manage the best as i can, and be as perfect of a sweetie as i could be for them until something is realized or my brain moves on to the next obsession.