While much of spiritual progress is beyond the rational, the field is beginning to validate old tools and even describe some new techniques.
Researchers have begun to look into what makes people happy. This new "happiness research" is, of course, in the tradition of many great thinkers of the past. Basically, Positive Psychology finds that individuals have "set points" of happiness or typical levels of happiness that we tend to return to after things - good or bad - disturb us. These set points are only tendencies however. With awareness and a certain amount of effort, they can be changed.
One of the first researchers in the field is Mihaly Csikszentmihalyi, author of Flow, the Psychology of Optimal Experience. Much of the territory was described by Maslow a generation earlier, but Csikszentmihalyi began to do research and describe the results in detail.
The research consists of training a group of volunteers on a reporting technique and then polling them randomly as they go through their normal day. What emerges is a picture of what types of activity produce the most happiness. The results show that activities that challenge our abilities and experience result in a state of flow. In the state of flow, people are less aware of time, less ware of their own day-to-day worries and more aware of the task at hand.
Csikszentmihalyi goes further and develops a "self-help" methodology for people who want to increase their ability to spend time in this state. The main headings of Chapters 5-7 of Flow give some idea:
5 The Body in Flow
Higher, Faster, Stronger
The Joys of Movement
Sex as Flow
The Ultimate Control: Yoga and the Martial Arts
Flow through the Senses: the Joys of Seeing
The Flow of Music
The Joys of Tasting
6 The Flow of Thought
The Mother of Science
The Rules of the Games of the Mind
The Play of Words
The Delights of Science
Amateurs and Professionals
The Challenge of Lifelong Learning
7 Work as Flow
The Paradox of Work
The Waste of Free Time
Religions, Values, and Peak Experiences: Abraham Maslow
In this book Maslow describes the connection between "peak experiences" (similar to what Csikszentmihalyi would come to call "flow") and spiritual or mystical experiences of various religious traditions. Unlike Csikszentmihalyi, Maslow does not support his theories with research, he states them as things that should be obvious.