The speaker, who asks to be called Mez and begins with a plea to "trust me," is asking for something that sounds generous but turns out to be a little smug. Rather than being criticized, Mez wants the listener to look for what is good about their approach. Only after the listener has tried things their own way, and presumably failed, are they invited to come back for advice.
The last line gives the game away. "I told you so" sits alone, as if Mez has been waiting the whole poem to say it. The earlier lines pretend to be patient and open, but the ending reveals a need to be proven right.
The mood is dry and wry, with a hint of defensiveness. The poem is funny because it is so familiar: anyone who has argued over whose way is better will recognize the speaker's stubborn pride.