In my experience, much of our suffering is needless and self-inflicted. What is sadder still is that we keep on repeating the downward spiral of destructive desires, thoughts, actions and consequences which destroy us and our relationships. We must mature to the point where we are not unduly crushed by accidents and difficulties. We are not here to be comfortable, but to grow through experience and the getting of wisdom. Life is the place for gaining experience and some of our most valuable ones are simultaneously the most difficult.
Life is uncertain.
We walk by faith and we can't tell whether we will live or die from moment to moment, or if those whom we love will go or be taken from us. Happy people recognise these sorts of facts and go on anyway. Life includes unfairness and injustice. Although we embrace truths, life will not always be fair. Neither should we expect it to always be so in some childish way.