U is Uncertainty
Can you guarantee anything? The stock market? Return on your property investments? Your spend rate when you retire at age 35? No. You need to live with a little uncertainty. Spread the risk. Don't shove all your money in pension funds. Don't go all the way on your buy-to-let stratgey. Don't rely on the sale of your business. Get a good mix. Minimise uncertainty, then get used to living with it.