It is called Jesus Calling by Sarah Young. I find when I miss a day of reading, it is what I needed to hear that day.
Sample from the book: July 10
Relax in My Peaceful Presence
Do not bring performance pressures into our sacred space of communion. When you are with someone you trust completely, you feel free to be yourself. This is one of the joys of true friendship. Though I am Lord of lords and King of kings, I also desire to be your intimate Friend. When you are tense or pretentious in our relationship, I feel hurt. I know the worst about you, but I also know the best. I long for you to trust Me enough to be fully yourself with me, I am able to bring out the best in you: the very gifts I have planted in your soul. Relax and enjoy our friendship.
Revelation 17:14; John 15:14-15