Ageing is inevitable. How we age is not. That’s the message of the book From Strength to Strength: Finding Success, Happiness and Deep Purpose in the Second Half of Life, written by the Harvard professor Arthur C Brooks, already a bestseller in the US and published in the UK next week. Brooks suggests that our contentment levels in later years largely depend on the choices we have made in the preceding decades. To prove this he draws on the Harvard Study of Adult Development, a project started