Answer and Explanation:
I believe this is a tongue-in-cheek comment. As a matter of fact, this type of comment depends on our perspective in life, on how positively or negatively we tend to see things. Maybe a more positive person has noticed one day that he enjoys things that come in pairs. It may just be a coincidence, but he turned it into some sort of rule, of philosophy even.
I once heard somewhere that disasters come in trios. That means, if something bad happens, you can expect two more bad things to take place. Of course, this is not true - the same way that good things do not necessarily come in pairs. Maybe a person who focuses more on the negative side of things once payed attention only to disasters and tragedies occurring around him. Maybe he noticed three bad things and took them as the rule.
Anyhow, this type of comment is fun and harmless. It helps us make sense of the world we live in, as if we were able to understand things - good and bad - and perhaps even have some control over them. But it should not be taken as a serious remark.