Earlier quoted context omitted.
Let's make sure we are talking about the same thing. I don't mean the fleeting joy of a pop cycle on a hot summer day when you were twelve and the cutie you have a crush on smiled at you. I'm talking about a general disposition. A "happy person." It is the way one looks at and approaches the problems and/or situations. You can choose to change how you approach the problem and you can choose what you find rewarding in…
A lot of this “choosing to be happy” as the way you describe it though is merely self-deception/lying-to-oneself. If I’m starving - I have every right to be upset. Yet in your mind - I should just learn to enjoy the search for food (even if it doesn’t exist) rather than being upset that I’m literally dying.
Since you bring up starving, I'll give you my starving story. BMI was under 18 and trending south. I got kind of abandoned for a bit in high school. My daily food was one potato in the morning (baked, plain), the high school free lunch, and, as long as I stole an extra hamburger that I could sell (which was not every day, depending on rotation), I'd have enough money to get a can of soup for the evening. This would be warmed on a wood burning stove that I also used to keep my room warm. The rest of the house was, literally, ice cold due to a missing wall (which is non-ideal in the mountains and also encourages wildlife to steal your meager food stores). What meager food I could stash away got stolen by raccoons once - there was a missing wall on my house at the time and the mountain wildlife could come on in if they could navigate a tarp.
I could have been upset with my dad for leaving me in that situation. I could be upset with other extended (and close by) family who did not help. I could be upset with neighbors who didn't help. I could be upset when I saw people wasting food (and, yeah, that stung... a lot). I could be upset that my stomach being in pain or some stints with nausea was a normal feeling. I could be upset by a thousand things in my situation (and these are but the surface of my hardships). I could have decided that my happiness was based on all that.
However, I tried to enjoy "roughing it." I took the time to enjoy searching for wood to heat my wood burning stove to heat my cold room and my can of soup that I got only because I stole and sold other food earlier. Would I prefer that to where I am today? Hell the no. I looked around and knew I did not like where my life was directed and the current state of it. So I focused on what I could do. I could get my school work completed. I could talk to friends before school if I got there early enough. Maybe a day was a no-hamberger-available-to-steal-and-sell day; I would enjoy that I got to sneak a slice of pizza from another classroom's party or I could get the left overs from a friend before they tossed something. I think I was a generally happy person despite all of my hardships (and these are but the surface of my hardships).
So I've been starving with every right to be upset. I chose to, instead, focus on things I could do something about. Slowly I improved my situation. I found food. I got good grades. I got scholarships. I starved some more. I worked crazy hours. I failed. And I failed some more. By my late 20s, I had started to figure things out and I, for the first time, could buy a pizza on the way home and not think about the financial hardship. I could avoid being hungry. Tack on another decade and I am wildly successful. However, I've also had to deal with depression, anxiety, insecurity, and feeling like not belonging along the way.
Edit: post question I meant to ask:
> self-deception/lying-to-oneself
I'm curious on what you mean here - why is that significant? This sounds like saying you shouldn't read fiction because it isn't real. When you pump yourself up (for a lift, a sports game, to ask out someone attractive), you are practicing forms of self-deception. Also, you are not saying, "this is great, life sucks." You are saying, "life sucks, but there are great things." Reality doesn't change, but the way you interpret it can.