The majority of my training was in Transactional Analysis and it is normally the basis of my work with clients.
Transactional Analysis (TA) is a theory of personality and a psychotherapy focussed on personal growth and change. It was originated by Eric Berne, a Canadian Psycholgist who believed that people made "survival decisions" as small children which resulted in thoughts and beliefs about themselves, others and the world. These decisions influenced the child's ways of behaving in order to get needs met. He called these patterns of thoughts, feelings and behaviours our "script".
As adults these ways of behaving, thinking or feeling sometimes get in the way, but Berne believed, as they were based on decisions (albeit early unconscious decisions) they could be replaced by better, more effective decisions.
The most well known idea from TA is that of Parent, Adult and Child (You may be familiar with the idea of the "Inner Child")
The most important philosophical belief which underpins TA is that people are born "OK"
This means both you and I have intrinsic worth, value and dignity. I accept myself as me and I accept you as you. This does not mean that we necessarily accept and approve of each others' opinions or behaviours, but that beneath those opinions and behaviours we recognise the person and the value of that person's humanity.
TA psychotherapy is a shared experience. You and I together share the responsibility for you making the changes you want to make in your thoughts, your feelings and your behaviour. You change what YOU want to change, not what I might think would be good for you!