IF LIFE IS SO SHORT! SHORT.... I would use "..." instead of "!", because using the word if to start a sentence implies that there will be two parts to a sentence (eg. If I go, then I will be tired). This is called a conditional sentence, and you need to include the conditional second part. You can end it with ... to show the reader that you will answer this conditional phrase. So even though you don't show the second part, you allude to it. Does that make sense?

Are you scared of death? I was, but after losing a close friend, I realized that I am not scared of death anymore. Life is so short. We never know what will happen tomorrow to us, to you. or to anyone else.Yesterday they our friend (I would identify who "they" are, to make it more clear. I am assuming it was your good friend.) were was still with us, smile, smiling  with us, but today they are gone. That's life!
Do you know why I am not scared? of death? (To make the sentence more natural you don't have to write of death again, because it is already understood.) Because I don't think death is the end of everything. It's just the a new begining. After dying, I could be a wind, I could travel anywhere I want, even around the universe. I could watch my family from the clouds. I could whisper to them that I love them and they are always in my heart.
But I know they would will never hear. So why do we have to wait until we die to tell them we love them? Why did I had have to wait until my friend died to tell him that I loved him?. And now, I always regret because I did not telling him that being his friendship is was one of the happiest things I've met experienced in my life.
Don't let yourself be open to regrets after some one passed passes away. Let's start to tell them the important people in our lives, (Who are they?) that you we love them now! (You changed the perspective of the preceding sentence from "us" with let's to "you", you should keep it consistent.) Because life is so short!

I really liked this journal, it was written with sincerity. It was also very easy to read and sounds like how a Canadian would express themselves. Keep up the good work! :)