What is the one constant in your life? The one thing that has been there with you from your earliest memories, with you both in dreams and in waking, and even dare I say, in dreamless sleep. That does not change, is not subject to moods, is unaffected by all that you do but rather is the witness of all that happens to you. The answer: Consciousness. It is this consciousness which proclaims: I exist.
What is the nature of this consciousness? Bliss. Or if you will, joy. Fix yourself in this delight of consciousness. In its light all else is experienced, and it alone abides, detached, unaffected by events, however frightful, pleasant or somewhere in between. Remember a random event from your past. Think of the memory in exquisite detail. Does it make you feel a certain way? Or do you just remember being there, witnessing it? Live today like you remember the past, as the witness, calm and serene, regardless of how events may have shaken or stirred you at the time of their occurrence.
You say, I don't remember this consciousness that I am before I was born, or even in the first years of my life. The answer: Do you remember every single day of your 10th year, or even of the first half of this year? Of course not. If you did you'd remember exactly what you were thinking this very moment one year ago today. Do you? No one does. But you do not deny that you existed on those days you cannot remember. It is the same with consciousness. The vehicle may change (mind and body), but the reality I am is always here, always now, for it transcends both time and space.
Don't identify with the body that changes, nor with the mind which has its moods and fancies, and not with the particular set of circumstances you call life. All this is subject to change, to growing old, and eventually, dare I say, will die. But the I am - known as THAT - the Is-ness, pure existence consciousness bliss, which you are, is forever the same. Perfect. Complete. Reality.
The wave is the world, the foam is the individual, but you are the ocean from which all emerges.
Live as though you know this - or should we say, THAT. Because THAT is what you are.