A financial plan is a snapshot of the right decisions for your circumstances at one particular moment. The problem is that almost everything that goes into that plan keeps moving after the ink is dry — your income, your goals, your family, the tax rules, and the markets your money sits in.
A pension contribution strategy that made sense three years ago may no longer reflect your current allowance. An investment portfolio built around a 15-year time horizon needs revisiting as that horizon shortens. A protection policy taken out before you had children may no longer reflect what your family actually needs to be protected against. None of this means the original advice was wrong — it means that financial planning is an ongoing process, not a single event.
A pension is a long term investment the fund value may fluctuate and can go down. Your eventual income may depend upon the size of the fund at retirement, future interest rates and tax legislation.
The value of investments and any income from them can fall as well as rise and you may not get back the original amount invested.