I can honestly say (as will most men) that the single largest waste of our time was chasing girls in our youth. A friend of mine and I often noted that had we spent the same resources, time, energy, and finances pursuing doctorates or careers, we would be immeasurably better off, and arguably with the same level of success with women. The "repriortization" or "depriortization" of women in your life is not only key to the success of every young man, but ironically, the key to being successful with women. Merely "chasing girls" does not build character, galvanize you, give you skills, or make you into the man women seek out. But pursuing your own hobbies, interests, careers, and education does, ironically meaning if you want women, don't make them a priority.
Still, I had a client ask an interesting question about when did I realize the time and resources spent pursuing women was not worth it and the story is of value for any young (or old) man today.