If you are suffering from excessive worry or depression, learning to be present moment focused can bring the joy back into your life.
The difference between living in the now and living for now is about enjoying the moment rather than trying to make it a great moment.
Accepting the past is key to living in the present. This means that you admit that the past is over, you did the best that you could at the time. Now, the most you can do with the past is to allow yourself to learn from it. Make better decisions right now.