Newton's third law of motion states for every action there is an equal and opposite reaction.  The law of cause and effect is based on this principle.  Nothing is born from nothing.  Every effect has a cause, and every cause has an effect.

If we strike an object (cause), it goes hurtling across the room (effect).  If we do not pay attention to what we eat and how much we exercise (cause), we may gain or lose weight and suffer physical consequences of that reality (effect). 

Whatever we send out into the universe will come back to us in one way or another.  Some call it cause and effect while others refer to it simply as karma.  When we think certain thoughts and find ourselves vibrating on a certain frequency, that frequency radiates back to us and becomes the reality of our lives.  

When we have negative thoughts, we are causing a negative effect in our lives.  We will draw in more negativity, things won't go as planned and we will not be living the happy, fulfilling life of abundance we are meant to live.  When we think positive thoughts and cause ourselves to take positive actions to draw in positive results, the effect is a happy, positive life spent living in abundance and happiness.

The law of cause and effect is important to recognize and embrace because it signifies for us that nothing happens by chance in our universe.  There is always a reason, always a cause to every effect.  We may not always know the cause or fully understand it but one always exists.  To know this law is to know we are not helpless pawns subject to the uncontrollable whims of a vast, unfeeling universe or vengeful deity.  We are energy, we are power and we have so much influence over our own lives.  No, we can't control the ocean or stop a tornado (not yet anyway), but we can understand how they work and why.  We can learn to move within the realm of things we can control, and we can recognize the power of our actions to create effects in our lives.