To me, the reason for our existence is more a question of "how" rather than "why". We are here because the cosmological constant of our universe permitted the emergence of galaxies and their evolution led to our creation. If the energy of this cosmological constant was any higher or lower, we would not exist. It isn't hard to conceive the existence of other universes, but, not all of them have necessarily stumbled upon life.
Our place in the Milky Way happens to be an ideal breeding ground for abundant life - at least the Goldilocks zone that the Earth happens to be in. Our planet's tilt is also favourable for our life to endure and evolve for a long time. It is like a warm dirty surface where bacteria thrive the most. There is probably intelligent life elsewhere in the universe, but you can bet that Earth is like a needle in a haystack. The life we may find elsewhere may be mostly bacteria, then a percentage will succeed in evolving animal-like or plant-like life before natural annihilation, and, an even smaller portion will have evolved intelligent life like our own or even more advanced.
We must also remember that the life of each human individual here on Earth is microscopically short compared to how old the universe is and how much it will extend ahead. So my philosophy is to make the most of it and learn as much as you can about this wonderful reality while you still can. If there is an emotional gap to be filled deep within me, it is not with the falsehoods of religion or superstition, but rather, science. Even if you are not much for scientific detail or have no interest in becoming versed in scientific knowledge, I bet that you will love keeping up with recent discoveries and breakthroughs.
Rather than believing in something that has never been proved and seems less likely the more we learn about the nature of things, why not take heed of what has been established already and wonder about the things that have not been solved yet? I'd rather listen to logic, reason without jumping to conclusions, and think freely for myself without being told what to believe if you catch my drift. The only life I am sure of is this one so I'm not going to ignore it or think less of it as I await in the promise of another hypothetical one born from wish-wash.
Death is coming whether we like it or not. The way I deal with it is by realising that I was 'dead' in the times of Aristotle, Rene Descartes, Isaac Newton, Albert Einstein and Kurt Godel and wasn't bothered by it one bit. And, whilst considering myself lucky to live in this amazingly technological age of science, one day I will go back to that non-existent state. The only thing I fear is a slow and painful process of dying. If I'm lucky, the process will be short. But death itself should not worry us because, after all, we won't know that we are dead. There will be no self to know. I often think of the following quotes among other witty ones:
"Life is hard. Then you die. Then they throw dirt in your face. Then the worms eat you. Be grateful it happens in that order."
- David Gerrold
"The fear of death is the most unjustified of all fears, for there's no risk of accident for someone who is dead."
- Albert Einstein
And finally, ask yourself if you would really like to live forever. Imagine an eternity where you can do everything you can possibly think of an infinite number of times. You would get bored shitless to the point of losing your mind. Imagine even thinking the same thoughts and feeling like there is no escape from the madness, as you realise that your eternity gradually kills the new and exciting. You would beg for a release... a release from the pain of being conscious for such a long time.
Now imagine that when you die, everything ceases and you are free from all experience... even your self. Remember those times when you sleep like a log. Well, to be dead is to be beyond that. And the amazing thing is that, while you are alive in deep meditation, you can experience a still-mind, free of concepts, and the realisation of one being intrinsically empty can be achieved. In meditation I realised that the less thoughts I had, the more blissful it got.
The Buddha came to a profound realisation in his meditative practice. He found that he could be anything in his mind, but, most profoundly, he realised that those concepts came from the intrinsic nothing inherent in all of us. The self, he found, is a strong illusion.