Self motivation is a very important aspect of all success. I continually encourage my clients to find their passion for the things they do. I ask them to do things like evaluating what they want, why they want it, and how they expect to get it. If it something that they truly desire to have or achieve, I direct them to think about making that thing important to themselves. This is done by regularly reminding themselves of why they want to achieve the goals or goals. It is a circle of mindfulness.
What I have done for clients in a similar situation was proposing to them to sign up for a race (5k, 10k, bike rides, biathlons or triathlons, half and full marathons, obstacle course race), so they still have a goal and purpose to keep training even when I’m not around. It reduces their stress levels and they slowly transfer that energy into training for those races. Of course I keep motivating them and make sure they stay on track with their overall fitness program.
All the previous answers were great. I thought I would add a few suggestions I did not see.
OVER SCHEDULED: If they are willing, get together with your clients and help plan out a weekly/monthly schedule with them. Effective time management can be very helpful in finding extra time in the day as well as prioritizing what is really is important. It can also be fun for you and the client to look through the schedule and find out where certain tasks/events can be combined with exercise/activity, i.e. shopping with a 40lb bag of dog chow. This technique can be initially time consuming to set up for both of you but very effective in the long run. A trusting relationship is key in gaining an honest schedule.
STRESSED!: For this obstacle we could implement stress management techniques. Get a list of about 3 different techniques, exercising being one of the obvious choices, rate them for effectiveness and time consumption and let the client choose which one to do each day. By allowing choice we promote self-control, or locus of control, and self-efficacy, for the client while reducing the effects of stress. Over time we hope the client will see the exercise technique as more effective and specific to their original goals.
Good luck Kim and when in doubt have fun.