system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why is it so easy to fall asleep on your couch even with desperately trying to stay awake, but after dragging yourself to bed, you find yourself wide awake and unable to get back to sleep?
gpt
I think this is a psychology rather than biology question. 

The answer will vary from person to person but broadly it's likely to be that when you're on your sofa you're in your relaxation frame of mind so you can go to sleep but when you start your bed routine you start thinking about plans for the next day so you a/ get your brain working and b/ start worrying about how much sleep you need so can't relax. 

It's basically a 'sleep hygiene' issue, meaning your bed routine isn't helpful.