Most people treat pay, savings, mortgage, and debt as separate problems. In reality they interact: a pay rise can push you into a higher tax band, paying down debt reduces interest outgo, and a mortgage decision affects housing costs and liquidity. Treating items in isolation leads to surprises and poor trade-offs. The core idea, think in snapshots and paths Two straightforward mental shifts fix this: Snapshot: a single view of what you own and owe today (assets − liabilitie