I always think that creating multiple sources of income is the best way for you to retire peacefully. It is important as you no need to worry much even do not have to work anymore.
Multiple sources of income do not mean that you need to work for several jobs for multiple incomes. If you have more sources of income, then the more stable you are when facing global economy crisis. For example, when you loss your main job and most probably you will be jobless for few months. During this time, you still have passive income that can support your living expenses.