Posture is really, really important when it comes to sitting.
I do think there’s this (I don’t know where it comes from pictures I guess films) idea that we have to sit cross-legged on the floor. I recommend to everybody unless you have grown up sitting cross-legged on the floor and you’re very comfortable with that, or unless you’ve done a lot of yoga or gymnastics, whatever it is that allows you to sit cross-legged on the floor comfortably for a long period of time there’s really no need to do that when you’re meditating in fact you are already learning a new skill. So maybe it’s actually simplest just to sit on a chair. I always recommend you do it legs and arms uncrossed so you are sitting with arms just resting on the legs and as much as possible not using the back of the chairs. It is quite tempting naturally to sort of lean against the the back of the chair. If you can move towards the front of the chair and sort of tilt the hips a little bit so that the back sort of feels upright. The feet are flat on the floor you feel very grounded. If you struggle with that — and I’ve definitely, if I sit on a chair, I get this a little bit the back starts to kind of hunch over a bit — I find just a little cushion or a little towel underneath my back side just helps keep the the hips in place and then you don’t have to put any effort into sitting upright. The back just naturally sits straight. So it’s all about if you can set it up in the right way. It really doesn’t take any effort at all.
You don’t want to be sitting there thinking OK I must keep a straight back and equally you don’t want to be falling asleep and slouched over. So finding a chair which is upright where you have a nice balance of you know you’re relaxed but you’re focused rather than lying down on the sofa and falling asleep. It’s quite important and if you think about it the way we set the body up will very much influence the mind. So if the body is say, the body is lying down on a bed well the mind associates lying down being horizontal with sleep. And there’s a pretty good chance that we’ll drift toward sleep. Equally if we are too upright then the mind will be a bit uptight as well so it’s finding that sweet spot where we feel sort of comfortable, relaxed, and yet focussed at the same time.