Last night I had a LD in which I tried to do the nose pinch RC after I already knew I was dreaming (I looked at my hands). The weird thing is that it didn’t work, even though I already knew I was dreaming, and I completely expected to breathe through my fingers… I’ve used this RC before with success, but in my last 2 LD’s it hasn’t worked. I can’t explain why it didn’t work last night, because I know how it feels to breathe through my fingers… and I already knew I was dreaming…
I ask this because this RC is said to be one of the most reliable… Any explanations?
RC dont work all the time!!!
and maybe its just not the RC for you.it Vary from one to an other.
while i was reading Q dream diary i have found that she’s always using the pinch nose RC but it didnt work for a few dreams after she use it so many time.there is alot of RC around and you sould already have a backup RC.
Some RC’s don’t work for some people, and since you are used to the way things work in real life this can also affect the results in lucid dreams - you know that pinching your nose in real life will make it impossible to breathe through your nose, and if you think the same way in a lucid dream then chances are you will get exactly that result. 
I’ve always had major problems with pushing my hands through walls, but looking at watches and lifting heavy objects seems much easier.
You may find harder to breathe with the pinch nose RC.
I recommend always pondering about the dreaming state and expecting the RC to tell that you are dreaming before doing the RC.This way even simpler RCs can work in a very accurate way.
Also always have a backup RC as ghanemhaithem stated.
Here is my fool proof test (thus far). If there is ever a question of whether or not I’m dreaming…then, for sure, I know that I’m dreaming.
*disclaimer…do NOT recommend this technique if you have a loose grip on reality. Also, I’ve heard reports of very VERY advanced dreamers who begin to blur the lines between waking and dreaming and, in that case, I can’t imagine this technique being of much help. In fact, I can’t imagine anything being of much help in that situation other than some inner state of resolve that allows one to keep one’s shit together amidst total mayhem 
thanks for the replies! I guess I’ll have to try it next time I have a LD… As you said, I usually do at least two RC’s before deciding whether I’m dreaming or not. Recently I’ve been trying to come up with new RC’s like whistling. I recently had a dream in which I tried very hard to whistle and no sound came out, just air…