I reached out to my professor over winter break, 2 weeks before spring semester about being a TA for his class. I was planning to only work 1hr a week, and  I was also going to be working in another department for 4 hours a week. 

All the arrangements were set, and I was going start in week 4. 

On the first 2 days of the 1st week of the semester, I realized I was going to be too busy with school and outside commitments to handle the new TA position. 

So I emailed my professor and told him I won't be able to TA for the class any longer. And I apologised for wasting his time and his classes time. 

I feel so awful for doing this. I'm afraid of running into him. 

Ahhuugh

How big was my mess up? 
Is there anything I can do to redeem myself? 

I guess I lost out on the letter of rec he said I could get if I needed. 