I want to talk about the 'pay yourself first' principle from the operational level, because the abstract advice doesn't help much.

Pay yourself first means your investment contribution happens before any discretionary spending decision, not after. Concretely: on payday, an automated transfer moves a predetermined amount to your investment accounts. What remains in checking is your operating budget.

The implementation detail that matters: the transfer should happen before you see the full paycheck balance. If you see $4,200 in your account and then manually decide to transfer $500, willpower is involved. If your account shows $3,700 because $500 already moved, there's nothing to resist.

For people who feel like they can never find extra money to save: this is the mechanism. You don't find extra money — you make a permanent precommitment and adjust your lifestyle to the post-transfer balance. The adjustment happens automatically within 1-2 pay cycles.