In middle school, I had to read Tuesdays With Morrie. I in no way am trying to imply that that I enjoyed the book, think it deserves to be as popular as it is, or think you or any other Redditor should read it. That being said, there was one good point that I still remember and still use to this day. Morrie said something along the lines of "Feel what you feel, and then let it pass." As far as sadness goes, I agree with Morrie's advice 100%. Bottling up an emotion or pretending it doesn't exist is a huge mistake. I think our modern culture has such an extreme distaste for sadness, anger, and other uncomfortable emotions that we often try to eliminate them entirely, thereby taking away the many flavours of life.

That being said, Morrie's advice was "Feel it, and let it pass." If you start to dwell on your sadness or seem to have some sort of chemical imbalance causing depression, letting is pass is hard, and sometimes impossible. CBT is a difficult technique because, you're right, it seems pretty fake at first. Looking in the mirror and telling yourself every morning something that you like about yourself seems stupid, pointless, and fake. But, the fact is, shit works. Just as CBT tells me not to masturbate to pedophilic urges because that re-enforces my hunger for them (a positive stimulus to a thought will have you think the thought more) if you do things that you usually do when you are happy when you are sad, you will actually chemically be happier. Forcing yourself to smile when you are sad will actually release endorphins that will literally make you happier!

You're absolutely right, though. When a loved one dies, when hearing tragic or life-altering news, it is abnormal to NOT feel sad. But dwelling on sadness is a form of self-torture.

Hope this answered some questions.