You’ve got a spreadsheet to automatically track and calculate those percentages. 60, 20, 10, 10. It all adds up. Then the market does what the market does and it’s all fouled up. 58, 21, 13, 8. No!!!!
Many investors have a curious need to tinker with their portfolio. I literally only mess with my parents’ portfolio twice a year. First, to rebalance and second, to take a Required Minimum Distribution (RMD) out of the portfolio.