get the world by the tail

Before I Say Good-Byeを読んでいます。Jimmyはボート事故で死んだ4人の内の一人で、Jackは事故を調べている警察官です。
They sat stiffly across from each other in the small but pleasant living room. Jack made a point of studying the large framed family portrait that was hanging over the couch.
“That was taken in happier times,” he observed. “Jimmy looks as though he’s got the world by the tail, every inch the proud husband and father.”
"got the world by the tail" は世界を支配している様な成功者を連想させますが、どうでしょうか？　辞書で確認します。辞書には "has/have the world by the tail" の慣用句が載っていました。
・McGraw-Hill Dictionary of American Idioms and Phrasal Verbs: has destiny under control. The young businessman had the world by the tail with a downhill drag. He had made a million dollars before he was twenty-five. She's got the world by the tail now, but her fame won't last forever.
・Wiktionary: (idiomatic) To possess great influence and opportunity.: Usage notes: Also appears in such similar phrases as grab the world by the tail, got the world by the tail.
Often used in describing a situation in which a person possesses great, and perhaps excessive, self-confidence.