I understand the desire to make your case to them, BUT DONT DO IT!!!
Whatever biblical argument you make, you will be seen as an apostate. Whatever emotion you show, you will be viewed as angry or troubled. Whatever personal reasons you give, you will be ignored and they will imagine a more JW-friendly explanation.
You are not dealing with healthy minds & you will NOT be understood or given fair consideration.
If you see a JW, just smile and keep walking. Say you are in a hurry & keep moving.
If you must talk to them be kind, positive, and generally upbeat and get away from them ASAP. Be vague about stress, depression, exhaustion, illness, or whatever you choose. BUT DONT SHOW ANY EMOTION, it will be used against you.
Dont worry about the contradiction in saying you are ill or depressed and acting positive & upbeat, they will not notice. They arent really paying any attention to you.