Rumi isn't simply celebrating optimism or positive thinking—he's identifying where our actual limitations originate. The pointed accusation ("except in your mind") suggests that we don't fail because circumstances are narrow, but because we've constructed invisible walls through habit, fear, or inherited assumptions. Consider someone who learned as a child that "people like us don't become artists" or "our family doesn't travel"—decades later, when circumstances change, their mind hasn't caught up, and they remain fenced in by a belief that costs nothing to maintain. The garden itself remains boundless; we're the only ones drawing the property lines.