Don't worry, be happy!
1. You will finally learn the material from undergrad
2. You will be a superior communicator
3. You will have teaching experience on your CV/resume
4. You will have better interpersonal skills
5. You can virtuously procrastinate
6. Your schedule is more structured
7. TA-ing boosts your confidence
It can be very demoralizing.
TA-ing can be the bit of work where you actually succeed!
Share your TA experiences in the comments!