Impact of Behavioral Biases on Wealth Management Decisions

John is a high-net-worth individual seeking assistance with his investment portfolio. He has accumulated significant wealth from his technology startup and is now looking to diversify his portfolio. However, John exhibits several behavioral biases, including overconfidence in his own judgment and a tendency to hold onto losing investments because of a psychological aversion to realizing losses.

As his wealth manager, discuss how these behavioral factors can impact John's investment decisions and overall portfolio performance. Additionally, provide strategies to mitigate the effects of these biases and help John make more rational investment choices.