Roosevelt reminds us that happiness isn't a destination we arrive at, but rather a sensation we experience *while doing*—and crucially, the doing must involve both accomplishment and invention. Most people chase happiness as though it were an object to possess, missing that the actual pleasure lives in the struggle itself, not the finish line. A musician who spends weeks mastering a difficult passage knows this in their bones: the real joy isn't playing the finished piece for others, but those incremental moments when their fingers finally obey what their imagination demanded. He's saying we need both the measurable victory and the creative risk—happiness requires us to be neither drifting dreamers nor joyless strivers, but people genuinely *making* something difficult real.