"I can feel guilty about the past, apprehensive about the future, but only in the present can I act. The ability to be in the present moment is a major component of mental wellness." -- Abraham Maslow
"Only in the present can I act."
Only -- I can't act in the past or future. So there's no point in worrying about them, except to take action in the present to make amends for the past, or to take action in the present to prepare for the future (although that one is tricky, since the future is a variable.)
in the present -- I read once that in the months after the Kennedy assassination, Mrs. Kennedy was inundated with requests/offers for causes she could become involved in, work she could do. She felt confused and overwhelmed, and asked a priest she trusted which she should pursue. "Look in your lap," he said to her (supposedly -- I don't know if this story is apocryphal or true.) What was there? Her children. Since I heard that story, I have sometimes asked myself, "What's in my lap?" and have found it a very clarifying way to proceed. What needs taking care of now, this minute?
can I -- No point in worrying about things I can't do and options I don't have. And no point making up projects for other people, since they are not under my control. What can I? What can I? Where does my power lie? How can I use it?
act -- Thinking is good, but acting gets things done. I should not act without thinking, but if I think without acting, I'm wasting my time, the precious present.