I don't know any specific reason why.
The whole getting set work and having a specific date to give in gets me anxious. Socialising gets me mildly anxious/makes me very uncomfortable,one of the reasons why is because it's extremely difficult for me to look at people while talking.If I take a day off from school then I don't ever feel like going back because I'm scared of the reactions I'll get.
There are A LOT of little things that make me very anxious.(I don't know if it helped but I hope it did somehow)
btw sorry for the late reply :/