Mental prayer in my opinion is nothing else than an intimate sharing between friends; it means taking time frequently to be alone with Him who we know loves us. The important thing is not to think much but to love much and so do that which best stirs you to love. Love is not great delight but desire to please God in everything.
In my deepest, darkest moments, what really got me through was a prayer. Sometimes my prayer was 'Help me.' Sometimes a prayer was 'Thank you.' What I've discovered is that intimate connection and communication with my creator will always get me through because I know my support, my help, is just a prayer away.