Almost everyone prefers $100 today to $110 in a month, while also preferring $110 in thirteen months to $100 in twelve. The preference reverses with distance, which means it is not a coherent preference at all: it is a disproportionate discount applied to the future.
Applied to money, it is the engine behind almost every decision later regretted: buying on installments, deferring the first contribution, "I'll start investing next year". And it is especially expensive with compound interest, because the year postponed is the one that would have worked hardest.
Since willpower does not fix it, architecture does: automate the transfer on payday, raise the percentage when a raise arrives, and put friction where the impulse is. A decision made once beats a decision made every month.