The Vietnamese Buddhist monk and philosopher, Thich Nhat Hanh, writes about enjoying a god cup of tea. You must be completely awake in the present to enjoy the tea. Only in awareness of the present can your hands feel the pleasant warmth of the cup. Only in the present can you savor the aroma, taste the sweetness, appreciate the delicacy. If you are ruminating about the past or worrying about the future, you will completely miss the experience of enjoying the cup of tea. You will look down at the cup, and the tea will be gone. 

Life is like that. If you are not fully in the present, you will look around and it will be gone. You will have missed the feel, the aroma, the delicacy and beauty of life. It will seem to be speeding past you.

The past is finished. Learn from it and let it go. The future is not even here yet. Plan for it, but do not waste your time worrying about it. Worrying is worthless. When you stop ruminating about what has already happened, when you stop worrying about what might never happen, then you will be in the present moment. Then you will begin to experience joy in life.