here's the deal for me with taking things like softball seriously vs not taking them seriously. there has to be some kind of happy medium. taking them too serious is ridiculous but you at least have to try or else what's the point. basically if there is a team vs another team and someone is getting paid (ref, score keeper) then you're obligated to kind of try. if not then you aren't.
If you wear baseball pants, you're probably taking it too seriously. Batting gloves, maybe.
If you cuss out an ump over a call, you're taking it too seriously.
If you are genuinely angry at a teammate's performance, you're taking it too seriously.
If you do a quick tag on a guy even though he is obviously safe because that's what you were taught in little league, you're taking it too seriously.
Hustling out an infield single or diving for the occasional grounder, you're OK.