Finally I succeeded! After some succesful and many non-succesful attempts of lucid dreaming, last night I managed to do it!
In the evening I did some thinking or shall I call it meditation, to concentrate on my dreams to come. This was the result: in the middle of the night I thought I was awake, but everything felt different, better. So I said to myself "this feels almost like being awake but it can't be, so I am in my dream".
Then had the best dream in loooooong long time.
I was on the sea, in a boat. There was something bad under the surface, a submarine or giant octopus or Ludovician shark from Steven Hall's
Raw Shark Texts. I was trying to get away from it. The bad was not overwhelmingly evil though, more of a nuisance or minor negative thing. All in all, something to avoid.
Not even my full speed was enough to escape the shadow underneath, it kept following my every turn. Then the dolphins came to rescue. I hovered above the sea surface, hopping from one dolphin back to another so that the thing below wasn't able to follow my path.
After the evil was mislead and disappeared, I turned to dolphins and asked them how could I ever thank them enough for saving me. The dolphins just laughed friendly bubbly laugh and told me it was their pleasure. Nothing to mention about and I was very welcome, any time.