When she says she is exhausted....say yes I know this is very tiring. It is normal to feel the sadness you are feeling...she feels it too. I felt the same thing when I took the twins on a vacation with out my W.
When you feel your confidence slipping just become "neil the teacher" again with regards to your confidence. In order to lead a class of students you need to have a lot of confidence otherwise they will they will eat you for lunch (no matter what age they are). I know I had a short stint as a substitute teacher after grad school and before going in the coast guard.
TwinDad Me 39, W 36, M 11 W - MLC, WAW???? 2 Kids B/G 3 YRS Old Start of the Long and Bumpy Road..... On the verge of piecing.....a new beginning