I asked him out, he decided to just stay friends, but I can't and don't wanna ruin our friendship HELP!!!

We've been friends for two years, and I've liked him since i first met him, but feel more comfortable knowing him, so we became friends and this year our "flirting" really picked up. I dropped hints asking him about homecoming, buying him a thoughtful birthday present, and asked him on two group hangouts and to the sadie hawkins dance. However, he said he acts that way toward everyone, and said i asked him outta no where and he just wants to stay friends. I was crushed, and at first angry and hurt but i felt bad taking it out on him. I'm trying to get over him, and now i get frustrated but then feel guilty because i still like him so much but now seem more clingy and am trying to let go!!! How do i get over him and still stay good friends? How do i stop the pain from hurting inside everytime i see him, but still smile on the outside like nothings wrong? Please help!