Motivation to keep working out when you are older is a tough thing to manage. You need to keep fired up to get through the down days emotionally and the days when other things overwhelm us all.
Think of it this way...if you do work out, even if it is a modified shorter or lighter routine, you will feel so much better afterwards. Your emotional state will be better, your energy in a better place, and your stress level will dissipate.
The thing about stress and emotional issues is that they contribute to inflammation on our systems, one big cause of heart disease, cancer and other problems.
Working out can be a stress and inflammation reliever if not overdone, or abusive.
So get motivated and do it right and DON'T HURT YOURSELF!