I made a discovery.

I succeeded in WILD two nights back. And I failed in WILD last night. I wondered, how can this be possible, even though I made everything the same way. Then I remembered what I had done differently:
(Night 1 means the night when I succesfully WILDed, and Night 2 means the night when I failed)
During night one I slept for 4hrs, and I stayed up for 6mins. Back then I was sleepy but my mind was clear.
During night two I slept for 5hrs and stayed up for 3mins. Back then I was not sleepy but my mind was dizzy.

So:
Sleep little, stay up alot. This way your body will be sleepy but your mind will be clear.
And as a side tip: Use autosuggestion to make your mind even more clear.

NOTICE:
This may not work for everyone, but it works for me.