Be passionate!
One word - passion. God sent his only son for us so what's going on with the lack of enthusiasm for Him?
Remember how you felt when you first became a Christian. You felt as if you could take on the whole world and save them all. Now where has this passion gone?
I know for some Christians at times (including myself) find it difficult to get enthusiastic about going to church, worshipping or even picking up a Bible.
This is a rant to say that God never loses his passion for us so why should it become difficult for us? I know the trials we are faced with daily but God cares enough for us to help us through them.
Just remember back to the time you first met with God and how life changing it was and keep that on your mind next time you are struggling to keep your faith enthusiastic!