This is from my little treasure trove of things copied from the web - I don't know whose words they are but I find this a useful prayer/meditation.
"If I am emotionally vulnerable, Lord, if I am easy prey for those who would beguile or deceive me for their own selfish reasons, I earnestly pray for Your protection. Teach me how to prevent others from manipulating me by their smooth talk and apparent friendship. Help me perceive lies and falseness before a harmful situation develops. In all my involvements guide me, Lord, that I may learn to distinguish between what is fact and what is simply my own wishful thinking."