A critical part of any habit change plan is having measurable outcomes. It is hard to be successful if can’t measure it. It is important to come to some agreement with your client how you are going to measure their achievements.
As a coach, we need to encourage your client not worry about a temporary set back. The main pathways in the brain have been driving our habits and behavior since childhood. Your client needs to realize that it requires energy and time to change a habit. Explain to them it is just like rebooting their computer.
When your client starts again, you can always add something new that helps them.