I was thinking about this today because of another thread. Like many ex JWs, I struggled with finding a way to make life meaningful after losing a belief system. What I have found works for me is to strive to make each day count. I am not going to save the world, but I can make each day as meaningful as possible, in my own small way. If I only talk to three people today I can try to connect with those three people and in some small way make their day just that little bit better, by listening to them, by being positive, by helping them in some way if I can, and often I find that someone invariably gives something back to me in some way I never expected.
It's amazing what you start to notice when you stop living in the future and start looking around at what life has to offer right now.