If wrist pain has you coming out of poses like Down Dog or arm balances like Crow and Sage, I'm not surprised. Our wrists rarely bear more weight than a plate of food or possibly a purse. Asking your wrists to take most of your body weight is a big request. I'm not saying your wrists can't handle the challenge, but aside from gradually working on the duration you hold postures and letting the muscles surrounding this joint strengthen, here's a little tip I learned from my first Ashtanga teachers to prevent pose-induced pain.
When you are in a pose bearing a good bit of weight on your hands, take pressure out of your wrists by transferring weight from the base of your palm to your fingers. Spread your fingers as wide as you can and slightly cup the ground; press both your fingertips and the knuckles at the base of your fingers firmly into the mat along with the heel of your palm. Though the movement is subtle, this technique spreads the weight through your entire hand, making it a strong base for weight bearing.
This active-finger technique works in any posture when you're leaning into one or both hands, and it also increases your stability when balancing on your hands. Your fingertips can act as brakes to prevent teetering in poses like Half Moon or Handstand. Try this tip the next time you practice and hopefully it'll help take your mind off your wrists and bring it back to your breath.