First I would say: Try not to go to bed with a negative emotion. If you feel you failed, chances are you will fail. If things don't work out as you like, try telling yourself that it is ok. The best thing you can do at that point is go to sleep and have a good night rest. Just leave it be.

Secondly, don't put too much faith in the technique. It's not the technique that get's you lucid, it's you. The technique's only help you a bit a long. Even if you don't fall asleep while reciting mantra's or whatever technique you are doing, you still have the intention to Lucid Dream. Just that can be enough to have a Lucid Dream. So even if it doesn't work out the way you'd thought, just let it be and believe that you will have a Lucid Dream anyway.

I know I tried using mantra's and I fail at them. I still got some LD's from just the intention though

That's my 2 cents as a rookie