Be out of (one's) depth phrase
To be in a state of affairs that is too difficult for you to handle or comprehend.
I am a monolingual person. Therefore, when he asked me in a foreign language, I was out of my depth.
At that time, I was only able to ride a bike, so when he told me to ride a motorbike, I was out of my depth.
This expression alludes to being in water so deep that one might sink. It dates from around 1600.
To keep optimistic or have hope that something positive will occur and simultaneously prepare for a negative outcome
All I can do is hoping for the best and preparing for the worst.