Religious hypocrites "pretended to be righteous" in order to "trick" Jesus or "catch" Him in something He might say or do that was wrong. Imagine the irony! They pretended to be what Jesus actually was in order to catch Him doing the very thing they were intentionally doing! They were so blinded to the reality of their own hearts.
When we pretend to be something we are not, we are no different than those hypocrites. What are we trying to prove? Who are we trying to impress? We might be able to fool and impress others, but Jesus is never caught up in our deception. Wouldn't it be easier on all of us if we would just tell the truth and be who were are?
Pretending to be something just because we want to be something, doesn't actually make us the thing we are pretending to be. That is what children do.