Staying positive is not that simple. This is the common notion of most individuals especially those who have been going through difficult times more often than the others. Exhibiting a much inappropriate and negative behavior is considered by many as a much easier to have rather than being optimistic in times of troubles, pain and grief.
Life is never easy and that is a fact. However, you must also admit that there are those who may have been born with all the good things in their life. They may have the talents or skillsets which you may have wanted for a very long time, wealth, power and many more. These may be true but you have to also realize that all of us have gone through our own set of ups and downs. Problems happen to everybody and not just you.