Breathe. Pay closer attention to what you are doing. If you are reading, pay attention to the shapes of the words, the space on the page, the words, the emotion the word is triggering, the emotion the sentence is triggering, and slowly move to the next word, and the next, without skipping forward in haste.
So many of our daily challenges are down to moving too fast:
We make mistakes because we overlook details; we give in to impulses because we don't notice them until it is too late; we eat too much because we don't give our bodies time to signal that we're full.
It is very rare that you lose out by slowing down. That is not to say that you should stop giving in to impulses, but be aware of them and recognize them. Be aware of the moment, and recognize opportunities and jump at the impulses that benefit you. Go up to that beautiful woman and say hi, instead of mindlessly adding a chocolate to your basket when you're buying food just because your blood sugar was low then and there.
Mindfulness is the art of paying attention moment by moment; to recognize the truth and reality behind the veil of twisted rationalizations that your brain puts up.
Start by simply sitting down and pay attention to your breath for 5 minutes. Don't force yourself to suppress your thoughts, but whenever you notice your mind wandering, bring it gently back to notice your breath.
Think it is easy? Try. Set an alarm for five minutes, and notice your in breath, then your out breath, and so on, until the alarm goes off. If you're anything like me when I started, your brain will start yelling at you in various not so subtle ways after a minute or less to try to get you to stop being so stupid and let it get on with thinking. Or you will "wake up" after suddenly having gone off on a total digression for most or all of the five minutes.
Try again. And again. It will teach you willpower. It will teach you things about your impulses and subconscious you never knew.