For all of us, it is natural to feel sad when someone closest to us passes away, or get angry when someone does wrong to us. But have you ever encountered a person who feels "happy" amidst such situations? I guess it would be me, but we're more than 7 billion here on Earth now, and it's very possible to find even just one who's like that.
American psychiatrist Elizabeth Kubler Ross authored "Stages of Change," a book that discusses how a person normally deals with his life problems in general. According to the book, there are 5 stages that a person goes through every time a negative change (problem) happens in his life: Denial, Anger, Bargaining, Depression, and Acceptance. Taking for example a man's grief over his girlfriend's death due to a crime-related, a sudden situation, say a freaky shooting spree, the "moving on" process goes like this:
DENIAL: "It's not true! She's still alive!"
ANGER: "Why the heck this thing happened? Of all the people, why her? She doesn't deserve this?"
BARGAINING: "If I was just at her side the moment it happened, then I would have saved her."
DEPRESSION: "I should have died with her! I'd rather take my life than live without her!"
ACCEPTANCE: "I know she's not here anymore, so I guess I should get over this and move on."
In some cases, especially the extreme ones, going through the "moving on" stages can take longer periods of time than expected depending on the gravity of the situation itself and/or the impact made to the person involved plus the actions he had taken during the process. Subsequent negative actions usually prolong the process include - but not limited to - habitual drinking, drug abuse, and suicidal attempts, all leading to the person's death if not handled accordingly.
On the other hand, the "moving on" process can also go faster, although skipping the stages in-between Denial and Acceptance is not possible. The faster recovery from negative change depends on how the person handled himself positively in all aspects - physical, emotional, mental, social, and spiritual, among others - and how he understands both the situation itself and this "healing" process (best learned beforehand). People with such abilities adapt the principles of "mind over matter" and "mind over heart."
The human brain actually works in the same fashion as the computer's processor which commands consequent actions to the machine. Thus, the human brain has the power to "tell" everything the person should do including how he should emotionally react on various life situations - a clear opposite to the popular belief that "the heart dictates our emotions." However, the sets of actions that the computer's processor performs can be altered via data manipulation; and so with the human brain via conditioning and acquisition of new knowledge. As mentioned earlier, if the person, at the first place, has accepted the harsh realities of life including the existence of death and suffering, understood the process of "moving on" from negative change, and has the ability to make and maintain a positive outlook out of the various adversities of life, then the person's emotional recovery can go faster, thus his life would go back to normal at an earlier time. Just think of how Miss Philippines quickly stood up from her accidental downfall onstage in her icy-blue frock at the Miss Universe 1999 preliminaries and you'll see what this means.
Yes, it is human nature to feel sad or angry upon the situation's call, but such circumstances don't really tell us to dwell on them forever. Also, it is not the situation that makes us react accordingly but just us ourselves. Sadness and anger, among all other negative feelings, are just options; and having said that, happiness can also be a choice. For the narrowest of minds, being happy amidst negative situations is evil and tantamount to hoping for the worst for other people; but in reality, it is about finding the brighter side of even the worst things in life and looking forward to it with a smile.