I'm worried that I applied for a job at a warehouse but I don't think I'll be able to handle the work.
I am not sure I understand. Why are you so concerned about the job?
I just don't think the physical labor is for me.
IF you think that this job at warehouse is not suitable, you shouldn't have applied for it. Anyway if you think physical labor is not for you, you shouldn't join.
I told my mom and my sisters that I applied for this job, they are counting on me to get the position.
It is best to only apply for jobs you are sure you will be able to handle. Don't you want to succeed once you start working?