Perhaps a goal could be to write one letter a month for Amnesty International? Or a like organization. Or just to write a letter to the editor on a weekly/biweekly basis? Someplace to start expressing your views and concerns. Take part in political actions, set a goal of one each season, having the internet really helps in finding specific meetings/protests/discussion groups that cost only your time and your intellect/feelings. Just take One interest at a time and make one commitment to do a specific action.
I too have great difficulty with specifics---and I have found that I have to literally take one day at a time now to get things done. Sometimes I can go further afield but it is hard. I miss a time long ago when I had commitments (political and social) that just drove me to Be There and Do or Say something. (and am proud to have an activist daughter...who never knew her mother as such, but who hasn't suffered MI and is out there working on changing the world with vision, determination, and education...)