If you are depressed you are living in the past.  If you are anxious you are living in the future.  If you are at peace you are living in the present.

Don’t let yesterday take up too much of today.

Do not dwell in the past, do not dream of the future, concentrate the mind on the present moment.

In books lies the soul of the whole past time.

He who controls the past controls the future. He who controls the present controls the past

The secret of health for both mind and body is not to mourn for the past, worry about the future or anticipate troubles, but to live in the present moment wisely and earnestly.

Happy is the person who knows what to remember of the past, what to enjoy in the present, and what to plan for in the future.

The timeless in you is aware of life's timelessness. And knows that yesterday is but today's memory and tomorrow is today's dream.

Our consciousness is almost completely preoccupied with memory and expectation. We do not realize that there never was, is, nor will be any other experience than present experience.

I, not events, have the power to make me happy or unhappy today. I can choose which it shall be. Yesterday is dead, tomorrow hasn't arrived yet. I have just one day today and I'm going to be happy in it.

In the process of letting go, you will lose many things from the past, but you will find yourself.

Let go. Why do you cling to pain? There is nothing you can do about the wrongs of yesterday. It is not yours to judge. Why hold on to the very thing which keeps you from hope and love?

Live in the present, remember the past, and fear not the future, for it doesn't exist and never shall. There is only now.

The reading of all good books is like a conversation with the finest minds of past centuries.

Yesterday is gone. Tomorrow has not yet come. We have only today. Let us begin.

It isn’t what you did in the past that will affect the present. It’s what you do in the present that will redeem the past and thereby change the future.

Past and future exist only in our memory. The present moment, though, is outside of time, it's Eternity.

We are living in a culture entirely hypnotized by the illusion of time, in which the so-called present moment is felt as nothing but an infinitesimal hairline between an all-powerfully causative past and an absorbingly important future. 

They say I'm old-fashioned, and live in the past, but sometimes I think progress progresses too fast!

I can only note that the past is beautiful, because one never realises an emotion at the time. It expands later and thus we don't have complete emotions about the present, only about the past.