The Humanistic approach developed in the 1960's as a critical reaction to the technical emphases of both psychodynamic and behaviorist learning approaches to psychology. Drawing deeply from work done in the fields of existential and religious philosophy, the humanist psychologists staked a claim to the idea of a "client centered psychotherapy" (rather than a technique-oriented therapy). According to major humanists like Carl Rogers and Fredrick Perls, people were born knowing how to be healthy and were naturally drawn towards making healthy choices. These healthy natural impulses were thwarted by parents, teachers, religious leaders and other authorities acting on a variety of unhealthy (dysfunctional) culturally endorsed convictions, or (more sadly) from abusive motives. The job of the therapist was to help their clients to overcome the negative influences of authority and society or abusers and get back to making their own healthy choices which would support their growth. With loving care and support, people would be able to "fix themselves".
The humanist vision of what healthy growth might look like is a tolerant and essentially liberal one. The direction of growth should be driven from the inside (rather than according to society's needs) so that every human being is able (if they are lucky and do the necessary work) to become all they were born to be; to fully explore their inborn interests, and to make a unique contribution to society. This theoretical pinnacle of self-expression is referred to as a "self-actualized" state.
There are a whole range of conditions that must be met before any person can work on becoming self-actualized. According to the "needs hierarchy" described by Abraham Maslow, people must first secure their basic "organismic" needs (including adequate food, clothing and shelter necessary to keep themselves alive). Having achieved the basics, they next worry about and work to achieve: a feeling of adequate safety, a sense of belonging (to one or more social groups and relationship), and a sense of self-respect and social respect. Self-actualization, the drive to do all that you desire to do with your life, is something that only emerges as a motivator of behavior after all the earlier needs are adequately satisfied.
In addition to being as genuine as they could manage to be with their clients, humanist psychotherapists developed a number of techniques designed to help their clients move past fears or social commitments and responsibilities that kept them too frightened or too dutiful to think about pursuing their own inborn agendas. Realizing that many such road blocks took the form of an internalized sense of duty or of fear, humanist therapists developed many techniques that were designed to help people reconnect with their hidden, or suppressed wishes and dreams. Frequently, these techniques (including Perl's "empty chair" technique described below) worked at an emotional level rather than a rational one.
Humanistic psychology made a lot of sense in the 1970s during the height of the liberal "me" generation; it might look rather monstrous in the light of 21st century America which has become a far more conservative and conforming place. It is important to keep firmly in mind that the humanists were absolutely not suggesting that everyone should pursue any course of action that pleased them (such as child molestation, or murder). Rather, they were concerned that there were many people out there who failed to become artists because their parents urged them to become accountants instead; that there were many homosexually oriented people out there who were afraid to come "out of the closet" for fear of being rejected by family and society. Their philosophy was aimed at helping people to develop the benign and healthy parts of themselves that would otherwise get squashed by society so as to help people to become more essentially happy; it was not to encourage the development of monsters or sociopaths. The humanistic philosophy does encourage a sort of selfishness, but it is not the monstrous sort of selfishness of the narcissist, but instead the healthy mature sort characteristic of the happy fulfilled person who knows how to set limits and to be responsible in addition to being able to follow their bliss spontaneously without worrying too much what other people think.
The key insights to take home from humanistic theory are that: 1) achieving happiness is often a matter of developing the freedom for yourself to pursue your deepest interests, and that 2) there are many ways that your deepest interests can get sabotaged or buried. You will need to overcome any road blocks (which frequently take the form of either fear or duty) before you become free. Techniques that tend to be helpful in getting you back on track tend to play towards your emotions (helping you reconnect with your buried desires and feel their motivating force).