Abstract: Among other things, a method includes, on successive occasions over a period of time, gathering measured data and self-reported data that represent a health state of a particular participant in a health goal system, using the gathered data in a machine learning engine to select, for a current occasion, a current intervention to be self-applied by the particular participant, the machine learning engine having learned from data gathered from a group of participants on successive occasions, the effectiveness of sequences of self-applied interventions in improving the health states of participants who belong to respective groups that share similar characteristics, the current intervention being expected to affect, for the particular participant (i) a behavior, (ii) the health state, or (iii) a health awareness, and providing the particular participant, electronically through a user interface, information that will encourage the particular participant to engage in the selected self-applied current intervention.