1) Risk your life. Do something so close to the edge your heart is pounding in your ears and you can taste your life flashing by. (You have to mix it up though. Race cars today, skydive tomorrow, wrestle bears next month. Fear fades with time)
2) Get into shape. Like, really really good shape. The world becomes so full of life it's like it's on fire.
3) Get yourself lost, in the city or in the mountains, with nowhere to go and nothing to do for a day or two. Don't come home until said day or two have passed.