Last night, i went to sleep when i was very tired. I saw some dream that i can’t recall good and then i realized that i was dreaming. As soon as i realized it, i couldn’t see anything until i woke up. Could someone please tell me how to avoid this?
Moved from General Lucidness. 
That sometimes happens when you finally become lucid. You usually feel or looks like either everything is going to warp or fading to black and that means you need a way to keep your dream stable. There are different methods of keeping it stable but my choice is rubbing my hands together and telling myself this “I am lucid, I am dreaming, I am aware” for about as long as it takes to make the dream stable and do whatever I want in the lucid dream.
Generally something like that will happen in your first LD. Don’t give up hope though and keep trying and you will soon have amazing lucid dreams before you know it! Also, make sure your emotions are in check as soon as you know you are dreaming and try your hardest not to blink in a LD because multiple times when I have blinked I would close my eyes in the dream, but open my eyes in real life and wake up, it’s quite the bummer.