Why Do People Quit Meditating?
Your needs will change over time. A technique that fulfills your need in one season or year may need to shift to match your needs a season or a year later. So you need to reinvent meditation from time to time. Sometimes it's only a slight shift, sometimes the change is more radical.
As you fulfill one phase of your evolution, you will need to reinvent meditation also. Instinctive Meditation trains you to sense your own needs and adapt your meditation practice to fulfill your needs. You might crave solitude and silence for a month, then shift to wanting to party or have your life filled with socializing and music. Instinctive Meditation appreciates that life is always changing, and gives you tools to meet life head-on.
One of the main reason people stop meditating after having a consistent practice for awhile is that their life changes. They may have been depressed, and the meditation heals that and leads them out into life. So they need to drop the old form of meditating and invent a new one.
From what I have seen, people do not have a lack of "discipline." Regular people work long hours and juggle many chores - they have plenty of discipline. No, when people are not meditating it is not because of lack of discipline - it's that they don't have some piece of knowledge they need. The technique they were doing no longer fits.
Just like you can tell when clothes fit you and have room to move, not too tight, not too loose, you can tell when a meditation practice fits you. Don't force yourself, ever, to do a meditation technique that feels wrong or feels constricting. This is unhealthy.