From Comfortable with Uncertainty by Pema Chodron
"Being able to lighten up is the key to feeling at home with your body, mind, and emotions, to feeling worthy to live on this planet. For example, you can hear the slogan "Always maintain a joyful mind" and start beating yourself over the head for never being joyful. That kind of witness is a bit heavy.
This earnestness, this seriousness about everything in our lives--including practice--this goal-oriented, we're going-to-do-it-or-else attitude, is the world's greatest killjoy. There's no sense of appreciation because we're so solemn about everything. In contrast, a joyful mind is very ordinary and relaxed. So lighten up. Don't make such a big deal.
When you aspiration is to lighten up, you begin to have a sense of humor. Your serious state of mind keeps getting popped. In addition to a sense of humor, a basic support for a joyful mind is curiosity, paying attention, taking an interest in the world around you. Happiness is not required, but being curious without a heavy judgmental attitude helps. If you are judgmental, you can even be curious about that.