Unless someone printed this tip for you, you are using a computer right now, or your mobile.
How are you sitting?
Are you comfortable?
What is the angle of your neck?
How is your back aligned?
Are your shoulders tensed or lopsided?
If you keep sitting this way for another 30 minutes, will you still be comfortable?
Did you change your posture as you read those questions?
What posture feels better for you?
Here is a diagram with the key points about how to sit when using a computer so that you avoid the postural conditions, and pains, that so many computer users develop. Compare how you are sitting right now with the diagram.
Most of us would greatly benefit from having a timer set to remind us to notice our posture, move, stretch, relax, and get up to walk a bit. Try it 🙂
My best wishes, Paul