John Cutter has owned a home in Toronto for the past 45 years. He is thinking of downsizing by selling his house and moving to a rental apartment for his retirement. John observes that housing prices in the city have grown at 7 percent annually over this period. Based on this information, he decides to stay in his house in order to enjoy future gains. What behavioural finance concept is John exhibiting and how is this influencing his decision-making?