The answer is to trust & let go!
If you've built up a habit of raising your larynx to change your pitch & using your constrictor muscles when you sing, it's going to require lots of focused intention to make a change. Learning to sing with a neutral relaxed larynx & open throat may be challenging at first & you may not like the sound of your singing to begin with as your body adjusts to this change but hang in there & stick with it!
The exercise in the video below will help you learn to sing those higher notes with ease & smooth out any unwanted breaks.
Tip of the day - Singing the vowel 'oo' encourages a low & relaxed larynx & an open throat.