1. A computer-implemented method of assessing and improving a user's life skills and self-efficacy for life stage readiness, comprising: providing a life stage readiness application which includes: a life skills measurement module, and a reverse engineering diagnosis module; providing a plurality of databases including: a life skills baseline score database for storing a numeric scoring system for scoring life skill competencies, the scoring system including a baseline score for each of a plurality of preselected life skill competencies and a composite baseline score for the plurality of preselected life skill competencies for each of a plurality of preselected life stage transitions, a life skills measurement database for storing data about the user's symptoms and other evidence of the user's mental and emotional health and life skill competencies of the user, and a reverse engineering diagnoses database for storing data of a plurality of human syndromes and disorders and other evidence of a human's emotional and mental health associated with each of such syndromes and disorders; using the life skills measurement module, collecting from the user via a user access device over a communications network data about the user's symptoms and other evidence of the user's life skills and mental and emotional health and storing such collected data in the life skills measurement database; assessing the user's readiness for a life stage transition based upon the collected user symptoms and other evidence wherein such assessing includes, in at least one interactive session with the user via the user access device over the communications network, measuring a plurality of life skill competencies, wherein the measuring of a plurality of life skill competencies includes generating quantitative scores based upon the numeric scoring system of the user's self-image, self-management skills, risk/reward predisposition, interpersonal skills, and existence or non-existence of one or more syndromes and disorders; using the reverse engineering diagnosis module, generating a plurality of potential differential diagnoses by comparing the user's collected symptoms and other evidence of the user's mental and emotional health with the symptoms and other evidence of mental and emotional health associated with each of the plurality of human syndromes and disorders stored in the reverse engineering diagnoses database; ranking the plurality of potential diagnoses using the reverse engineering diagnosis module from most likely to least likely; wherein the assessing of the user's readiness for a life stage transition includes: determining a composite score of the scores of the measured life skill competencies; and comparing the composite score to the respective baseline composite score stored in the life skills baseline score database for the life stage transition, which baseline composite score is predictive of the user's readiness or unreadiness for success in the life stage transition; upon determining that the user's measured composite score is greater than the baseline composite score, outputting to the user the measured composite score indicative of the user's readiness for the life stage transaction.