There are some people who take things in life too seriously. These people are usually party poopers and not much fun to be around. However, a person may be serious in one thing and not serious in another. It all depends on their passion on the subject.
For example, there are those that take sports seriously to the point of attacking rival fans, despite not having any relation to their favorite team other than being a spectator. Then there are those that get offended by certain things, and they get violent because of it. These people take things too seriously, and it offers no tangible benefit to taking things so seriously.