Do I have to be happy?

Over the past few months I have been doing a great deal of struggling in the past few months in dealing with all the things in my life. One of the things that's has resulted from this is questioning in my mind about whether or not one can have the Love and Grace of God and have a bad disposition. 

To put it another way, can not may and not should but is it possible to live a truly Christian life and do so with a bad attitude?  I am reminded of the words of Saint Paul in Phillipians where he talks about if his jailers kill him he will be with God and if they free him he can go on preaching God's word in the world and either way is a win. How can I read that passage, take it into me and not be joyous?  

Let me be clear about one thing. I am not talking about being grumpy or having bad days every now and again.  I am talking about despising what Godis calling me to do. I mean can I truly give my life to God, do my best to let my will succumb to His and be mad about it?