For this I usually present the following analogy.
When a dog goes out in the rain it probably remembers the last time it was in the same situation. It knows that it doesn't really like it and it knows that in extreme cases it might not have to go out at all when this happens.
What it will never be able to do is understand WHY there is all this wet stuff around when it wasn't there yesterday. It is way beyond its mental capacity to understand this, it just has to live with it.
What we as humans fail to come to terms with is that there are things which are equally 'way beyond' our mental capacity and which we will never be able to understand. Many of these things concern the universe, its origins, its extent, its workings and its future. We know very little about the concept of time, and gravity. We know it exists and what it does, but we have no idea why it does it.
We may chose to believe that all this was created by a supreme being, but then where did he come from? what did he build the universe out of? what was there before?
Like the dog who doesn't understand the rain, we will never have the answers to all our questions either.
Deal with it.