This study compares two approaches to helping people who are aging with MS or SCI and are experiencing depressed mood to become more physically active. The study is carried out entirely by telephone. There is no need to travel and participants may reside anywhere within the United States. We will examine the effects of the intervention on overall physical activity, mood, pain, fatigue and general health. Participants will complete surveys over the phone throughout the study and wear an activity monitor 3 times. The study is 6 months in length and participants may receive up to $120 for their time and effort.