Which ever dumbass that said "honesty is the best policy" is a fucking liar.
I read enough news articles to know this, if you want to preserve your freedom (that is, the very little remaining freedom that you still have under this ultra-capitalistic world), you have to lie, otherwise you will end up in a place wose than prison.
Therapy is usually voluntary, and the people going are going for a reason and that's usually to better themselves or help themselves in some way. So lying is just a massive waste of money and time.
If you wanna see an even more massive waste of time and money, just mention to the wrong therapist that you have thoughts of suicide. Then you get a nice 72 hour forced hold at a facility that will then charge you thousands of dollars for the privilege of being involuntarily held there.