It depends on the person that this question is asked, and the life they've lead up to the point of being asked. To a poor person with mental and emotional stability, a good life is just a life where you are financially stable and aren't threatened with starvation or eviction. To a poor person with a mental illness, a good life is one where you are happy, despite your financial position. A good life is to me, however, is a combination of both, where you are financially stable, emotionally stable, and mentally stable. So, in essence, the key to a good life is being able to make good decisions.
The first step to the good life is financial stability. The key to this step is realizing the difference between wanting something and needing it. You need to eat breakfast, but you don't need to spend $5.50 on a bacon, egg, and cheese sandwich and an iced coffee. You can just go to the cafeteria and get the free breakfast that is provided for you. You need clothes, but you don't need a $75 designer dress when you can get much more clothes at a much lower price. In order to be financially stable, you need to be able to decide what is best for you at your current financial status.
The second step is to find emotional stability. Emotional stability, to me, means that you feel at peace, calm, happy. In order to do this! you need to get rid of your stress, worries, and anxieties. This step is probably going to be the hardest, since most times we run away from our problems instead of facing them. However, accepting that you have a problem is the first step to recovery. In order to get rid of your anxieties, you need to find out why you're anxious about it. If you are anxious about a test, you are just afraid of failing and you should to study more. If you are afraid to tell your crush that you like them, you are just afraid of being rejected and you should wait until you know you can bear with pain of rejection.