Life is all about struggles and hardships. It's not that easy but not that complicated as we make it. It's just like the sun who is criticized for it's sunshine during the Summers and cherished for that sunshine in Winters. The path is always same, it's us who has to walk but in positive manner...
Sometimes we get so used to of someone's presence that we don't even realize that they won't be there with us forever. We stop cherishing our moments of togetherness, we start taking them for granted, and probably that's where we go wrong. Nothing lasts forever. One day everything will eventually become a memory. You'll look back craving for that person, wanting to relive those moments of togetherness. But you know what? The clock doesn't have a reverse gear. So value your present before it becomes a regrettable past!