Re: Hard to Stay in Seiza
Assuming you don't have an injury, but are experiencing tightness & discomfort in feet, ankles or knees - give yourself time to let the muscles get used to it. Make sure your muscles are warmed up (by walking, moving) before class, and do some gentle stretching after class.
What I did to practice at home the days I was not at the dojo was to kneel on a soft carpet and do some little task (for me it was brushing the cat) just for 2 minutes...when it was comfortable for 2 minutes, make it 2 1/2 minutes... etc. only increasing it by a little bit and only when it had become comfortable.