The Teaching of Thanissaro Bhikkhu

 "Ajaan Suwat would often begin his evening Dhamma talks by saying to put yourself in a good mood, to approach the meditation with a sense of confidence, reminding yourself that you're doing something that's very good. It may be difficult, but it's good. 

And it requires that you keep yourself in a good mood, no matter what happens, no matter how poorly it goes. Grace under pressure is an important skill in the meditation: the ability to smile to yourself no matter what happens--what the Thais call smiling in defiance of the tigers. That ability has saved a lot of meditators from going off course, getting discouraged, and letting their meditation crash.

So whatever comes up in the meditation, treat it with good humor. 

The ability to laugh at yourself is probably one of the most important abilities you have as a meditator. It's a matter of perspective, and also of balance. After all, you have to keep a certain amount of pressure on yourself as you meditate. This is an earnest endeavor we're involved in, but you can't let it get grim. Find out for yourself what exactly is the right amount of pressure to put on yourself and how to apply the pressure skillfully...

...When things don't go well, just drop whatever it is that's not going well. Move back to a level where you're pretty sure you can do things properly. And don't engage in a lot of recriminations, because they don't help anything at all. Just remind yourself that that's not what we're here for, drop it, and go on. 

When you develop this sense of good mood, you can ratchet up the level of pressure--the amount of time you spend with the meditation, the persistence with which you pursue it--without snapping. 

So whatever comes up in the meditation, whether it's good or bad or whatever, always try to keep a good sense of humor. Even when things seem to be going well, maintain a good sense of humor. Don't get swollen up with your importance or your accomplishment, because then you get complacent and it's easy to crash.

When I went to study with Ajaan Fuang, one of the first things that really drew me to him was his sense of humor. A good sense of humor usually goes with wisdom. The ability to step back and keep things in perspective: That's what makes you wise. It's precisely what you need as a meditator. So when things start getting grim, when nothing seems to work, just step back for a bit and try to regain your good humor. You'll find that that, more than anything else, will carry you through."

Good Humor

Thanissaro Bhikkhu

http://www.dhammatalks.org/books/Meditations3/Section0014.html