Your are your 'selfish' years. It's a decade to immerse yourself in every single thing possible. Be selfish with your time and all the aspects of you. Tinker with shit, travel, explore, love a lot, love a little and never touch the ground.
Start now. Start where you are. Start with fear. Start with pain. Start with doubt. Start with hands shaking. Start with voice trembling, but start. Start & don't stop. Start where you are, with what you have. Just start.