i find it next to impossible to stick to healthy routines without something external to act as a 'compass', too.

you have identified your sticking point: social interaction.

is there some regular thing you could get into a habit of doing that involves you interacting with people? martial arts springs to mind... because people get REALLY INTO it and train, like, many times per week...

you have also identified that you need something to feel passionately about... do you have any ideas about how you might find one for yourself?