Pessimistic Optimist or Optimistic Pessimist?

We started the fifth IDEM cycle last Tuesday evening.  We finished the last session in November, so it had been a long time since we'd all been together.  Unfortunately, the new materials weren't quite ready, so we continued our discussion from the last cycle when Ryan asked each of us to list one thing that we have difficulty overcoming in our daily walk.  Tuesday night's topic was "pessimism."  

Jesus teaches us that we should not be like those who have no hope.  Therefore, in the big picture, those of us who have eternal life, are not without hope.  However, in the small things, we often from move back and forth from the half-empty glass to the half-full glass depending upon the circumstances.  

The topic made an interesting discussion. . . . . if we trust God and are living by faith, is it a sin to be pessimistic?  No answers today, just questions.