Need help beating Garen as Riven!

So I like to play Riven quite a bit--she's a really fun champion... However, when it comes to matchup against tanky champions-especially Garen-I find this game just really boring and gives me crippling depression just by being alive.

Unlike other matchups like Darius and Renekton which offers an opportunity for counter-plays, Garen is just... really dull to play against. His kit is so linear that there's only really one way to play against him, and that is to kite and kite. (pretty hard as a melee champion like Riven when he can just silence you).

Other than the few rare moments where Garen misplays (if that's even possible on Garen), he would only to get even bulkier and tankier, making the matchup ever more boring. In addition, he would still output just enough damage to kill you cough his ultimate cough, which you can't really do anything against (especially when he has multiple armour items).

So what's a fun way to play against Garen?