Sound advice, but my experience was the opposite. i could land 180s all day before i could land a strait air. The only reason i could think of is because during a 180, im concentrating on the rotation, spotting the landing, and it generally keeps me occupied while in the air. When i was just trying to strait air over a jump i would get Air man arms and beef it because i would get unstable.
I would recommend trying a simple indy (back hand on toe edge) while you're in the air. Some people find that it keeps them more stable.