Ah, the key is not to shift in the front when you're in the top or bottom gear in the back. You could drop your chain or jam it up and go down like a sack of potatoes (been there, done that). My husband, who has been riding for years, taught me to always be about three rings from the top or bottom before making that front shift (in either direction). There is much less stress on the chain and front derailleur that way, and I haven't dropped my chain or missed a shift since I started doing it this way. The key is to anticipate based on the terrain coming up in front of you and shift up or down in front before you absolutely have to!
Good luck,
Emily