The ability to relax is often easier for competitive athletes. I personally feel that competitive athletes have an advantage in this practice because they know how to work hard and they know how to steady the work. They know things can be totally boring and boring and boring, but they keep working. Now if you haven't done much competitive sport, you can try to imagine a little bit about what it is like and if you can't imagine, go read a book about sport training. Read some of the advice they give, this "tuning of the stringed instrument" business.
How do we really know when we're too tight? How do we really know when we're too light, too soft? Many times if we relax, if we don't watch out, we can go too far.
And another way of looking at it is like, we've gone off balance and we've gone so far to the right, we bump into the wall. "Oh, I'd better relax". Yeah, and then we start to go the other way and we get to the middle and it's great but we keep going the other way and boom, we bump into the other wall. Sometimes it's just a matter of you've got to go and have your own Dukkha first. Okay, work so hard and you collapse finally? "Oh this is the time I need a break". Now, if you don't want the personal Dukkha, then it can be helpful to get a couple of those sport training books and read a little bit. Read about pushing energy and not pushing energy.
When you're getting tense, try to pick up on the body. A lot of people when they're tight, what happens? You know, it's classic. They grind their teeth. It happened to me in one retreat many, many years ago. After "x" amount of days (I have no idea how many so that's why I say "x"), somewhere around a third of the retreat, all of a sudden I discovered my bottom two teeth were loose. I couldn't believe it! I just couldn't believe it! I am not a nervous type of person but I was grinding too hard, I was pushing too hard, I was letting my teeth go loose. I just couldn't believe it. When I found out, I thought I'd better relax. Okay, I like my teeth, I'm already missing one, I don't want the whole set to go. So, that was it, my experience of Dukkha from pushing too hard. I had to let go, I had to relax a bit.
Now, mental Dukkha, pushing too hard mentally. Are you just stuck in Dukkha, are you stuck in a state that's yucky, you've gone too far, one way or the other? Try to see what the mental state is. If it's restlessness or worry then it's often pushing too hard. If it's sloth and torpor, it's often not pushing enough.
Those are also guidelines for you as to what type of mental state you have as to the Dukkha that you have. Pushing too hard, you get off balance, more restlessness. You can adjust the walking a great deal to relax. You can slow down, you can speed up, you can focus on the bottom of your feet, you can feel the whole foot, you can feel the leg, you can feel the body, you can walk fast, you can walk slow. Walking meditation is a wonderful place where you can adjust in order to relax. So experiment with the walking.
I will also say that if your sitting is getting tight in normal life, don't forget about walking meditation. For many people in normal life, walking meditation is something they rarely ever do, unless they are walking to a bus or something, and then they think that is equal to walking meditation. No, it's not. It's good, it's helpful, it's better than walking to the bus totally daydreaming, but it's not the same as back and forth, and back and forth, and back and forth. It's not the same. So don't forget about walking meditation in normal life to help relax.