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. We are sometimes controlled by forces we cannot master, such as the wind and the sea, or the domino effect of someone else's volition. Good things happen to bad people and vice versa. The honest are defrauded and felons walk free to enjoys their spoils.