I take solace in philosophy anytime I am confronted with questions like this. Two branches of philosophy that I find useful in answering this particular question are mathematics and observational science. Given the vastness of the universe, it is hard to imagine a universe where we are the only kid in the block especially if you use mathematical ideas such as theory of probability, order of entropy, etc.
But then we have to confront another reality which brings us back to observational science. To this date, we have not been able to observe and verify the existence of life much less the intelligent one outside of this planet. We (great apes) have been around on this planet for 20 million years, now. If there were intelligent lives besides our own, we would have heard back from them by now. May be they came in our distant past when we were not able to observe or communicate with them. May be the distance between them and us is so vast that it creates a natural barrier that cannot be overcome; if this is true, we will never make the contact. So it is quite possible that even though there are intelligent lives out there, we will never meet them.
We are very luck that things have been pretty calm in our neighborhood of the galaxy for past few million years which allowed major forms of life to evolve. This however, is not going to be the case permanently. As we know good chunk of life has been wiped out many times and then it evolved again; this has been repeated quite a few times now. The interval at which this mass extinction takes place is 65-million-year. Interestingly enough, this coincides with the vertical oscillation period of our solar system across the disc of our Milky Way galaxy. We are heading towards an assured mass extinction in less than 65-million years provided we do not get hit by an asteroid in the mean time. But let us say, we get luck, just for the sake of optimism, and we outlive all these extinctions, even then we will not be able to avoid the reality that the Sun will run out of fuel in few billion years and when that happens, continuation of life will not be possible in our solar system.
This life is precious and yet temporary. There is no eternal life. There is one life embedded in one chance we get. One moment is all we have to live our life in. So I say, "Peace to ya all!"
I agree to that. But one more thing. Possibly there are thousands or even hundreds of tousands of theoretically life supporting planets in our own galaxy. But there are restrictions for evolution. A big one is gravity. Double the diameter of the earth and you get 8 times the gravity. I would weigh then, say, around 600 kg. Baahhhh. This would make the evolution of a technologically versatile intelligence not quite easy. Very small people with very big problems getting something into space.
On the other hand we know that a little less gravity like on Mars leads to the loss of the atmosphere. Bad Karma.
Then, they could be on the other side of the disc. We don't even know how it looks like there because we cannot see through the core.
Next, we are in a position to emit radiation since around 100 years now. If they are at par in evolution with us it would take around 100.000 years for their signals to reach us. Or vice versa. If we should detect a signal, it comes from a very long time ago in the history of their planet.
There is absolutely no reason to fear aliens. I am pretty sure they exist, or have existed, or will exist. Somewhere. Only thar somewhere is for sure in a unimaginable vast physical distance.
Only religions woud have to change their stories a little bit should we find a proof for extraterrestrial intelligent life. Maybe so: god has set up different zoos for his entertainment.