For a worry free life, you must follow the natural laws. Otherwise, you could get into endless worrisome.
If you truly understand these, you will know how and what to do. The Boston bombing suspects apparently had wrong thoughts, that determined their wrong doing. Their thoughts controlled their doing. I smoked before, I did not know smoking is that bad. I now know it is very bad thing, so I totally stopped it. I even want my relatives to stop.
For example, you need proper rest, proper food, and balance of work and recreation. That is a law of nature. If you do not obey it, you can get damage to your health and you could get into endless unhappiness.
Hope you get the best in your life.