My eyes shut in lucid dreams? dream ends? help me D:

I've noticed in my lucid dreams, after I'm in it for a while my eyes start shutting. You know when you are super tired and your eyes just start shutting and you doze off? that happens in the LD to me and usually ends the dream. Like my eyes roll back.
Example. A few nights ago I had an extremely long LD. It seemed like 30 minutes or more, then about halfway through I started not being able to open my eyes, luckily I caught myself and said some voice commands and the dream continued.
Does this happen to anyone else? how can I prevent it?

I closed my eyes for the first time in a LD ever the other night to try something suggested by someone eles (Hyu) dream guide/partner (Yuya). (Check it out in my DJ if you want) I tried it, I closed my eyes and took in all the other senses around me and I was amazed how much more powerful and how many other things there were to feel!

You may be sabotaging yourself for some reason. Try to never think about this aspect because if you do then you will get it. Think of how much more heightened your vision CAN be.