I've helped quite a few students do this! I hope this helps ALL of you!!!
Do you ever notice that it's less that you "can't" sing something and moreso you won't sing something? No matter how much you want it, your body somehow won't let you have it?
Our voices are unique to other instruments because it has such a close tie to our physical health and emotions. Yes, it's possible to fake a smoker's cough and speaking voice, but if you met this person for the first time today, I'm sure (s)he isn't pretending to have that voice. Through listening to this person's speaking, you can hear years of abuse onto the vocal folds. Even things not so severe: how fast and hyper someone speaks after drinking coffee or slurred speech after drinking.
As far as emotions, you can plainly hear the emotions that are freely emitted. Some are skilled enough to perceive hidden emotions in the voice.
Similarly, can you tell when someone's lying? They want to say opposite from their brain's perceived "truth". That's where tells come from! The body is reacting because you're going against it's truths!
Side note: This is why I think some people are easily offended. "How dare you think differently than me and my reality!"
It's the same with the voice! If you wanna sing a high note, but your "truth" or belief is that you can't, your tell is way more obvious! You crack, sound strained, get shrill, etc!
You need to realign your beliefs with what you want to accomplish!
There's a meditation thing out there where they say to change your memories. Here's my take:
With each memory, there's two aspects: the event and how you feel about the event. You can't change the event. It already happened. What you can change is how you feel about the event. Revisit the event and "pop" that memory bubble. Reconfigure it into something else. You can choose to just see the event without emotions attached. You can change it to something more positive if you want.
Side note: I think this is where you get realists, optimists, and pessimists - event only people, event plus positive emotions people, and event plus negative emotions people. Most are geared to automatically create and perceive their memories as one of the three.
I've heard some horrible music teacher stories. Last night, I was talking to a coworker. She said she wanted to sing, but she was always afraid of the music teacher. Everyone knew that she was a mean, crabby bitch! My coworker never got into singing because of how she felt about this teacher! That is DISGUSTING to me! I read a story of a woman who never sang after her elementary school teacher told her to just mouth the words because she just didn't have a singing voice. She said she was sad and cried about it for many years. After emotional release, she was able to sing again for the first time in adulthood. This is so sad!!!
Similarly, each of you still struggling with singing have a mild form of this. I like to believe I'm an advanced singer, and I still come across these "tells" in my singing!
Remember, there's the event and there's how you feel about the event.
If you crack on a high note...the event is you cracked on a high note. Some may then feel they are unworthy to sing high notes. To perpetuate this feeling, they "on purpose" keep cracking on the high note to continue their belief.
Erase the emotions and focus on the event. You cracked. What happened? What can you do to fix this? If you want to add an emotion, a generic positive emotion is: "Great! Now, I am X - 1 times away from accomplishing my goals!" How many times do you have to mess up before being able to sing that high note? Who knows!? But it is definite you are one event closer to accomplishing your goals!
Quite simply, find what is wrong in your thinking and fix it so that your goals are actually attainable!
P.S. This applies to ANY goal you have in life!!!