It's not supposed to hurt

So if yoga is hurting you - either when you're in the class or the next day - I'm afraid to say it, but you're not doing it right. There's a way to get a stretch, and sometimes that will have a burn and sometimes you'll feel the next day like you stretched places that you haven't for a while, all normal stuff. But if you're skilled in how to use proper alignment, etcetera, then you can do just about any pose safely and without pain during or after (like leave the arms out of your triangle like I'm doing in this picture). That may mean your expression of a pose is shall we say, modest? However, you will still get the benefits of the pose even if you do it just a little bit!

Read Sam Dworkis' treatise on pain. He's an awesome teacher and taught me so much about pain and how to practise yoga while you're in pain or deal with chronic pain issues.