Today... A mindful exercise

If you keep thinking of yesterday and tomorrow, before you know it today will be gone
How much time do you spend thinking about what has already happened or what may happen in the future? ..... Our brain seems to be hardwired to think about past events and possible future ones to a point where we are very rarely present in the moment. 
Think about how much of today you spent not in the moment. Worrying about things that may not every happen or things that already have.
Before you know it your day has gone and you are lying in bed analysing all the days events that have already happened and thinking about tomorrows events that have not, and may not happen. Wow, sounds a little crazy when you look at it like that doesn't it. A life of past and future events going round and round.
Mindful Exercise
It takes practice to stop the brain doing this and to be mindful. A good place to start is by picking one thing you do daily, perhaps walking to the bus stop or station for work. You can even practice this when loading the dishwasher or cleaning your teeth.
Next time you take this walk or do a chore, concentrate on being present in the moment. Think about what you can see, hear, feel, smell, how the ground feels under your feet. Engage all your senses, this will help you stay present. If you find your mind wandering, bring it back to one of your senses. Ask yourself what am I seeing right now, what am hearing, how does it smell. You will be surprised at the things that you have never noticed on that same trip you take every day.
With regular practice your brain will start to get used to being more present in the moments which in turn will help you feel calmer and help regain some inner peace and quiet. 
Being mindful can really help with stressful situations allowing you to get out of your head for a while and quieten the mind.

Give it a go... become present in life, not an observer of past events and a predictor of future ones.
.