Living in the past or in the future deprives you of being present in the moment. 95% of unhappiness is caused not by what is happening in the now but what has happened in the past or you imagine may happen in the future.
Acceptance of where your life is at right now is crucial to your happiness. Comparisons can cause great unhappiness, comparing to where you were in the past or to somebody else or to where you dreamed you would be at this moment.
Accept what cannot be changed. Everything in your life is not going to be perfect, and that’s perfectly all right. Happy people learn to accept injustices and setbacks in their life that they cannot change, and instead put their energy on changing what they can control for the better.
The vast majority of the people on the face of this planet would gladly swap places with you right now no matter how bad you perceive your circumstances to be. It all depends on what other reality you are making your comparisons.
If your focus is on living in the past and what might have been, you can become a very depressed person. The day you stop wishing that the past was any different is the day you start to set yourself free.
If your focus is on living in the future your days can be filled with anxiety. Planning for the future is desirable but living in the future and imagining what can go wrong is undesirable. When something goes wrong in the present moment you can take some action to deal with it. The imaging thing that can go wrong in the future is much worse because there is nothing you can do, there is no action you can take to remedy the imaginary situation but actually to stop thinking about it.
The body can't tell the difference between an imaginary situation and a real situation, the body believes that you are threatened right now and produces a stress response. So, now you can understand why living in the now is important and crucial to your overall happiness. If there is nothing else you learn but just to be present in the NOW you will become a much happier person.
When you look to the past only recall great moments of happiness, when you look to the future only focus on what exciting things you can look forward to or plan or create strategies towards the achievement of your goals. Don't look back on the problems of the past (they can't be changed, you just keep re-hurting yourself each time you play the movies) and don't create horror movies of the future.
Believe that everything is going to work out fine in the future until you are proven wrong. It is only when things ACTUALLY go wrong are you in a position to take action to deal with them.