We can not change our destiny!

Well, first of all, it had been a long time since I wrote down any notes here.
When we talk about destiny , the first thing that cross our mind is the future. But in the past few days I have been thinking about that. Whatever thing we do, we cannot change our future. I mean, for example, we have plans to travel, but suddenly something wrong happened and then we can't go. But why did this happen?
Actually nobody knew the future and I have doubt if somebody could change theirs. It's true that everything changes, but the question is.. When ?