Irrecoverable losses

If an investment permanently loses 50% of its value, to get back to square one, your remaining investment needs to double in value.

If you're able to compound an investment at 5% for 14 years, it will double in value. So an extraordinarily bad investment can take over a decade to recover from.

This could happen if you invested in individual stocks, and are highly concentrated in a business which goes bankrupt. This is why investors diversify, to minimise the damage that a single investment can do to a portfolio.