Mine are:
You will go into therapy with one problem and realize you actually have twelve.
Therapy will take a lot longer than you think and it will be very hard.
You will spend a lot of time deciphering your feelings towards your therapist and much of the work is realizing those feelings (and any feelings) are okay.
There will be times when you will feel very alone in the process and only a sliver of hope and faith will keep you going.
There is a lesson and resiliency to be gained in even bad therapy.