Meditation posture is really important.
When it comes to sitting, I do know where we get this idea that we have to sit cross-legged on the floor, probably pictures. I recommend everybody that unless you’re very comfortable with sitting cross-legged unless you’ve done a lot of yoga or gymnastics or whatever allows you to sit cross-legged on the floor comfortably for an extended period of time, there’s no need to do that when you’re meditating.
Think about this, you’re already learning a new skill, so maybe it’s simplest to just to sit on a chair. I always recommend you do it with your legs and arms uncrossed. So sit in such a way, so your arms are just resting in the in the legs and as much as possible not using the back of the chair. I know is very tempting, we naturally lean against the back of the chair but if you can move towards the front and tilt the hips a bit so that the back feels right. Make sure your feet are flat on the floor. This posture will make you feel like you are very grounded.
Even with this seating positions, I’ve struggled. I’ve been there, I sit and all of the sudden my back starts to hunched over a bit. I find it very useful to use a little cushion underneath my backside; this helps me keep the hips in place, and then you don’t have to put any effort into sitting upright. Also, you don’t want to be sitting there thinking - okay! I must keep a straight back - and equally, you don’t want to be falling asleep so finding a chair which is up right where you have a nice balance of relaxing but focus rather than lying down on the sofa and falling asleep is vital.
The way we set the body up will influence the mind so if the body is lying down on a bed; the mind will associate lying down - being horizontal - with sleep and there’s a good chance that you will drift off to sleep. Equally, if we too upright in the chair, then it will feel a bit uptight as well so, it’s just finding that sweet spot where we feel comfortable relax and yet focused at the same time.