need help

I've been playing guitar about 5 years now and it's my favorite thing in the world and I think I've gotten pretty good over the years but when it comes to writing music it's a total disaster. i can write a billion riffs that sound cool and would sound good in a song but i never get past just 1 or 2 riffs it's like suddenly there's a big wall. so i'm basically just asking for any advice if anyone has any experience with this kind of thing or just has any helpful advice.