after-sex apathy

i have a strong tendancy to become really cold after sex. im a nice person, so i try to cover it up with niceties, but truthfully, i want them to go away and let me do other things that dont involve them pretty much the minute after we are done. im curious if anybody else feels this way and maybe has discovered the cause.i mean... im not just being nice beforehand simply to fuck... i just lose my give-a-shit after.