Writers; Inspiration, But No Way To Write It?

Have you ever had an excellent idea, for a story, or section in a story, but realize that it's really hard to get your idea past a few paragraphs. Like, currently, my MC, and a guy went moshing with Mutant Metalheads (evil), and when they got back home, their friend was acting all Momma-Bear overprotective (you'll both get distracted by metal (again) and get yourselves killed!) and sort of ashamed (what the h-e-double-hockey-sticks were you doing with the enemy?!) but I can't figure out how to make it...work? Does anyone else have this problem? Is there any cure?