Hello everyone ! First of all sorry for my bad English it’s not my maternal language.
I am new in the English forum but I don’t start Lucid Dreams, I’m just a foreigner and our forum is has been close… for 2 years now…
Anyway I have to ask you : How do you stay in you Lucid Dreams when you become lucid ?
Actually I do a lot of LD currently, without even train myself or using techniques.
Usually when I do a LD my subconscious react quickly to do anything, it excites me and then I wake up…
Unless in the last LD where I decide to control myself, then I concentrated and I made appear what I wanted. However it quickly disappeard and I woke up…
I know some techniques as looking at your hands or turning on yourself. There is something else I tried : I know you wake up when you are excited, so I put a hand on my chest and I could feel my heart pump really hard. I wanted calm me down but it didn’t work.
And last thing : Do you know how can I be in LD just like that. Everytime I’m dreaming and suddenly I realise it’s a dream.
Thanks. 
The way to stay in LDs when you feel them start to fade is to anchor a sense in the dream. Grab onto something and focus on the sense of touch you get, look at something and focus on seeing it.
Also try not to get too excited or emotional, it is possibly what is waking you up
Thank you.
More answers ?
Dream stability is very tricky as is dream recall. You may have stable and long LD’s and then again for no reason your dreams might start to collapse just after a few seconds after realization that’s a dream.
If you have this problem from 1st day that you started then it means that you just didn’t find the right way to keep your dreams stable. Techniques that are out there might help you or not. It’s very hard to say. But as you know the most common are: rubbing your hands, spinning, focusing on something, touching something and so on.
If you had stable and long dreams and they start to collapse after some time then it will stop after some time, for sure.
Meditation is another best way of learning how to become calm and focused which will help you to stabilize and prolong the dream. Remember that you can not be lucid in your dreams if you are not lucid in your waking life. (at least for some quality dreams)