As Karin suggests, have you ever tried keeping up with a Jack Russell terrier? Probably not. There is no way that you will ever motivate your spouse. The motivation comes from inside. She/he can watch you as you get ready for your workout, but unless the light comes on inside it will be short-lived. Just ask your spouse what is important.
I actually train my spouse. However, this is at her request and doesn’t always (more like rarely) work well with couples. I have been hired by other trainers to train with their spouses and family members though. If you go that route: show them how to pick a good one, don’t impose on their trainer (unless absolutely necessary) and be supportive, they need encouragement with impartiality.