If at this moment you have a problem, the great thing about living in the moment is, if one moment is not particularly pleasant, there will be another along right after it.
Dwelling on the past is a pointless exercise; no matter how hard you try your past will never get any better or worse for that matter. What is the point of reliving unpleasant experiences and feeling the pain all over again? Or longing for happier times you may have previously experienced. It is not real; it is in your head.
Worrying is another futile pursuit; often the problem is only imagined in the first place. I heard worry described as "Praying for something we don't want."
Even if a problem is inevitable, time enough to deal with it, if and when it arrives. Why torment yourself in the days or weeks leading up to the event? Remember with any problem; before the problem you were, after the problem you still are. The problem is transient, you are not.
How do you get to live in the moment? Ride your bike is one way, or practice meditation, but often we can slip out of the moment once we stop bike riding or meditating.
What worked for me was to become an observer of my mind; I become aware of my thoughts and recognized when I was slipping out of the moment and into the past or future. Just by being aware of these thoughts is enough to stop it."