A lot can be learned by examining the resistance to one's efforts to be happy.  I have paraphrased some of the responses I have had when I have told myself the following:

Try to be Happy:

• I can't be happy because that way I would accept things the way they are.
• I can't be happy because I have to push myself.

Try not to Worry:

• I have to worry in order to protect myself.
• I can't not worry because I might lose my job if I don't work hard enough and I won't work hard enough if I dont' worry