Thinking about the past with the intention of learning from life experiences to forge a better path or become a better person is a good idea. But most people don’t think back on their past with that mindset.

Instead, they dwell on the past and all the mistakes that they made. Or they think about how their life used to be and they compare it to now and feel like they’ve been short-changed.

Either way, it’s a way to cause stress. Thinking about the past can cause you to age rapidly. Living in the past leads to recriminations, self-doubt and blame. That causes emotional turmoil such as anxiety.

Discourses 4.12. 20-21 states What then? Is it possible to be free from fault altogether? No, that cannot be achieved, but it is possible ever to be intent upon avoiding faults. For we must be satisfied, if we succeed in escaping at least a few faults by never relaxing our attention. But now, when you say, "To-morrow I will pay attention," I would have you know that this is what you are saying: "To-day I will be shameless, tactless, abject; it will be in the power of other men to grieve me; I will get angry to-day, I will give way to envy." Just see all the evils that you are allowing yourself! But if it is good for you to pay attention to-morrow, how much better is it to-day! If it is to your interest to-morrow, it is much more so to-day, that you may be able to do the same to-morrow also, and not put it off again, this time to the day after to-morrow.

It’s the same thing with future thinking. You might not have a problem dwelling on the past but instead, you think about the future. You might feel anxiety about what’s going to happen to you physically.