I can't trust you.

Trust is a big, huge thing for me. It has to be, it is the basis of a relationship--platonic, emotional, sexual, spiritual, et al.
If I can't trust you, I can't love you in the only way I know how, honestly.

So don't fault me when I lie to you. I will not blame you for going away.
I didn't believe in you in the first place so I was not honest to begin with. 
The loss is yours, not mine.

Honesty is the best, the biggest, most important policy.