Why do people have regrets about things in their life?

My advice for people thinking about whether do something or not is to think how happy you would be if you chose what you actually want. It would be sad to sit down one day and realize you’re old that you didn’t get to do that one thing that you always dreamed of. As I said before, sometimes this decisions are out of our hands when we have to take care of others, as for example our families. The truth is that even though these things are important, you have to keep in mind that this is your life and it goes away one minute at a time, so you might as well find some time to accomplish those dreams. Now, sometimes we regret things that we thought they were a good decision in first place. Those are the kind of things that we shouldn’t worry about since we can’t change the past. What is done is done and it shouldn’t affect us that much. Live your life to the fullest and never stop to regret things.
Sometimes we sacrifice what we want to do for reasons that escape our decisions. For example, the protection of others or more realistic opportunities. When these things happen and times go by, we tend to think about what would have happened if we have done different. This can be very hard for some people to take if we consider this regrets as dreams that we pursuit all our life.