God is good and He certainly hears and answers our prayers! However, our relationship with God is not defined by our own feelings, but objectively by Jesus Christ. Of course, prayer and devotion make us more mindful of God and His Word, which sanctifies us, which is the good work of the Holy Spirit, but we have to be a little careful when talking about prayer, understanding that it's the fruit of faith, not the cause nor the sustainer of faith.
There are several prayer books in the Lutheran tradition. I own Lutheran Book of Prayer and Treasury of Daily Prayer, both of which are great! But we also pray from the heart. I saw this tweet yesterday by Pastor Will Weedon where he quotes Gerhard: "Whoever does not pray, in him faith fill will ultimately disappear." Prayer is at the heart of the Lutheran Church.