So a few days ago I think I had my first anxiety attack, I changed environment  and came to work for summer, it's my first time working as well,and I work as a waiter (13 hours shifts),7 days a week, I started 4 days ago,and I assume the anxiety attack was from exhaustment, the thing is I didn't feel necessarily anxious during the day,and when I went to bed it came out of the blue,now I worry that it could happen again,what could the cause be?