Mad,
Exhaustion is not unusual with anxiety. Lack of sleep, and the energy it takes to maintain amid the feelings of fear/worry/panic saps energy!
On days when you feel more energized...exercise is an excellent tool to manage anxiety.
However, if you are just wrung out...taking it easy, resting and doing relaxation/meditation exercises is going to be your best bet.
Here is the link to our Resources where you will find these great tools and more informative material for managing anxiety and feeling your best.
https://www.healingwell.com/community/default.aspx?f=9&m=104206
Keep posting, and we will keep you in support!
S.C.