I just finished reading an excellent book on marriage called "Love and Respect". I highly recommend it for all ages and stages of marriage. If acted upon, the principles in this book will transform your marriage. I've seen the results.
Here's a Bible verse that too, if acted upon, will transform your marriage. Are you ready for this one? It's a biggie:
Phillipians 2:3-4 Do nothing from selfishness or empty conceit, but with humility of mind regard one another as more important than yourselves; do not merely look out for your own personal interests, but also for the interests of others.