Ah yes- one of the most and incorrectly- cited verse by secularists in a hissy fit.  You do realize Matthew isn't declaring that the only way to pray is in private, right?  He's saying that unless you pray just as often and mightily in public as you do in private, then perhaps you're "in it" for the wrong reasons.

For example- you clearly enjoy reading and meditating on the Bible, and sharing its verses. Why else would you publically cite them to others?