Serious .. about the boredom of life

From the fact that I have read an informative and in-depth answers to the questions on doctor's forum, so I thought doctor might be able to help me.  I have a problem which is boredom, or maybe depression, don’t want to work, things that used to be fun turned to boring. I used to be the one who could say anything funny, make people laugh but I turn to be a person who say thing grudgingly. After spoken, it didn’t seem like I spoke it myself. Whatever I do, I feel so tried even for sex. I want a serious and in-depth answer please.

TroubleMan
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Answer
Let me answer your questions based on the information you have given me. Assuming that you may be fit with some of these differential diagnosis which are as followed
1. Just a normal boredom which mean, looking for happiness but not yet found.
2. The half-life crisis or midlife crisis.
3. Depression.
4. The state of boredom from the cycle of Samsara, can’t stand a meaningless of life.

Case 1 is typical boredom. From medical research, it was concluded that the factors related to happiness are
-    To have a meaningful life according to their religious beliefs.
-    Having a best friend or get married with a confidant. Some studies have shown that if we have a friend who finds himself easy to be happy, easy to laugh, we will also find ourselves easy to be happy. Or being with someone who we are satisfied with certain personality traits, is the real cause of hidden happiness.
-    To be busy doing something especially, something that utilize knowledge and skill at the full potential, the more  knowledge and skill applied, the more happiness it brings. And keeping yourself busy with an easy, inexpensive task brings more happiness than the difficult, expensive one. 
As for the factors that are not related to happiness.  Almost all researches have the same results.
-     To earn more or get rich.
-     Having high level of knowledge.
-    Being smart, having a high IQ.
-    Ages
-    Ethnicity
-    Gender
-    To have or don’t children

Case 2. Midlife crisis is a symptom of middle-aged person, approximately 40 years (30-50 years old). There is the change of feeling altered from the good feeling they have had to be the feeling of dissatisfaction with life or way of life, tired of people or any stimuli which once used to be challenged to oneself in the past and confused with oneself about who I am and where I am going to. If that's the case, your advice is to trace the five phases that Swiss psychiatrist Carl Jung gave, which are
-    A harmonious stage (accommodation) (before the age of 30-50) is the period that a person acts to be accepted, sometimes we need to wear a mask to hide our true self.  If the mask is very different from the real person adjusting to the crisis which will also be heavy on the half-life crisis.
-    The separation stage is the time when we start asking ourselves questions whether what our true self is like, Does it look like this mask?
-    The liminality stage. Rejecting the old self while still searching for the new identity feeling uncertain about who I am, which way to go, afraid to make a decision.
-    Creating a new accepted identity stage (Reintegration) discovering a new identity that is in harmony with real life, get more clearly who you are, which way to go and periodically reevaluate yourself. 
-    Facing the truth and accepting the unfavorable side that may still exist in a person (individuation), accepts that real life may need some pretending accept how to coordinate the expectations from people around you and harmonize them with your own needs. 

Case 3. Depression, According to the medical principle, antidepressants are used, but in your case, I recommend doing a lot of things without medication first, which are
-    Training the body to respond to relaxation regularly every day (relaxation response)  such as meditation or yoga  etc.
-    Change the lifestyle to promote health which are daily exercise (at least 30 minutes per day), get enough sleep and rest, reduce, avoid, quit stimulants such as cigarettes, alcohol, or even sugar.
-    Laughing and being a person with good sense of humor or try to get close to those who are good at laughing.
-    Expose to the sun, as sunlight can heal depression.
-    Change to positive thinking, associate with positive people.
-    Turn to do something that create some entertainment such as take time to go for a walk, listen to music or watch a funny movie, etc.

Case 4. The state of boredom from the cycle of Samsara. There is no scientific evidence to support how to fix this. I advise you to have a deep understanding of your own mind.  There are only four such activities: which are perception, think, feel, and observe. 
There are 2 kinds of occurrences for the 4 activities within our mind which are
(1)    Start then stop in just one moment but could develop a new one continuously like a flash, flash, flash, like the case where we think of things repeatedly and endlessly in a cycle.
(2)    These activities can only happen individually at a time. 
If looking back to our past, everything that makes us sad, unhappy, superficially, it seems like it comes from the outside, in the form of various stimuli that we accept. But if you look deeply, what makes us sad or unhappy, actually, there are only two of them, thoughts and feelings that was made to happen in our mind which we may feel like we are unable to stop it. When it will happen, must let it happen and had to endure it. But in reality, whether it is a thought  or feelings such as sadness, loneliness, feelings of worthlessness are just one activity of our mind which happen flashily, one flash then stop. But it seems like it can hold our mind all the time because it happened continuously like a flash, flash, flash. But if you consider the fact that this activity of our mind can stay only one by one, if there are other activity flashed into our mind it can cut off the prior existed thoughts or old feelings in our mind. And if other activity interrupt frequently as a flash, flash, flash, thoughts or feelings that make us sad, worried, unhappy would not born. When the cause of stress does not happen in our minds, stress or sadness will go away by what is interrupted to stop thoughts and feelings which is observing our own mind That means we can recall what we were thinking or feelings before, then followed by awareness that, as we are now observing our mind, we are conscious of not being distracted, if we often practice self-observation until fluently practice, we will be able to observe ourselves as often until many bad thoughts and feelings cannot take over our mind. That is .. to get over being sad.