It is really not uncommon for people to need help in the grieving process, and it seems perfectly natural to be grieving after the end of an 18 year therapy relationship. You may have only met with this therapist twice a year for the past 8 years, but I'm sure there was still that part of you that felt quite close to that T despite your actually distance from each other session-wise. Yours was an unusual therapeudic relationship; generally they don't go on for several decades. It is okay to need some help with this. It may be that you need some help, very possibly short-term, certainly shorter term than 18 years, to work through this loss.