The breath is the only thing you always carry. It does not require memory. It does not require faith. It is happening right now.
Every serious tradition — Zen, Sufi, Christian contemplative, Vedic — starts by turning attention to it. Not because breath is holy, but because breath is available.
How to actually do it
Sit upright. Close your eyes or lower them. Feel one full in-breath. Feel one full out-breath. That is one round. Count ten rounds. When you notice you have stopped counting, start again at one — without judgment.