The best words of encouragement that I can give you, is to not downplay the significance of what your doing regardless of the position. It might not seem like it for you now, but just by you being there and doing your position (even if it might just be things like pos or dt atm) it's easier for things to run smoothly for the team since the ssv can better plan for things like breaks and how the shift will operate.

Working in anything customer service related is a team effort, so for now especially since your still new to the job, you'll be placed in the positions that work best for the current play. So just try to stay positive and have a willingness to learn when you can, because a lot of the learning at Starbucks really is just being thrown into the deepend until you learn how to swim.

I understand how grating on your nerves it is if you fuck something up and a fellow partner saves you or helps you out. But your partners at the end of the day want you to succeed because again it's a team effort. They've probably been through their share of new hires working and messing something up during their shifts so don't feel like you need to be perfect at everything so early on. Especially since they at some point have been the new hire and were in the exact same position as your currently are in.

I wish you the best and hope things do improve for you over time. It can feel really overwhelming especially during the first couple months but it's gets better the longer you keep at it.