As a caregiver, how can I help motivate my dad to stick to his therapy goals?

Be sure to provide positive encouragement, pointing out even small gains. You might also try helping him to plan a realistic special activity that the therapy can help him to accomplish. The key is for it to be meaningful to him. Remind him as he makes gains in therapy that he is another step closer to achieiving that special goal. The activity does not have to be huge; it can be something very simple, especially to start with. Then build up to something bigger.