NLP (Neurolinguistics programming) uses mainly language to assess an individuals thoughts (conscious and sub-conscious). If you are truly happy in life, your are more than likely using NLP principles unconsciously without any official training. However, if there are areas you would like to improve, having better questions will bring about better answers.

As described on the website of John Grinder, co-founder of NLP

"Neuro-Linguistic Programming (NLP) is the process of creating models of excellence. Modeling is the complex activity of capturing in a learnable transferable code the differences that make a difference between an excellent performer and an average performer, between an excellent work team and an average one. NLP then is the process of identifying, coding and transferring precisely those differences in a learnable form to the interested participants and companies to allow significant upgrading of their performance to levels of excellence."

In short it is a systemised way of observing and learning from any person we see that is at the top. For example, to be the best surfer, one would want to go and watch and learn from Kelly Slater. Likewise in golf, using Tiger Woods would be a great model to learn from. By becoming who they are you can understand how they do things.

There is an understanding amongst researchers that we have a subconscious and a conscious mind. If you think about the subconscious mind as our libary of information, and conscious mind is what our brains recognise here and now. Due to the different partitions in our mind it is easy to focus on something at work (conscious mind) and forget about the pressure the office chair is applying to your legs, buttocks etc (subconscious mind). This concept is very important to understanding pain. If the threshold of pain is low enough it will stay in the subconscious (nociception). Once it exceeds the threshold of pain it becomes straight out pain. Both stimuli, nociception and pain, have a deleterious affect on the human skeletal and nervous system.