There's an old trick which W. Clement Stone used to live past 100. No, he didn't discover it, he just used it every day of his life. And of course, it disproves all these "guru's" who dump on positive thinking.
Stone was the past master of positive mental attitude - and was a Napoleon Hill student.
Here's what he said to himself in the mirror every single morning: "I feel good. I feel great! I feel TERRIFIC!!!"
Yes, that's out loud. Looking at himself in the mirror. While he said it.
And yes, you can do that, too.
This came up as an illustration after I listened to an old video by John LaTourette about Huna.
When you pay yourself a compliment (true or not), it makes the body stronger. Of course the true ones are more powerful because you believe it.
When you criticize someone else, you make yourself weaker.
So if you apply that Stone technique above, you immediately start off the day stronger. (An un-healthful state is simply weakness, isn't it? That's why this helps you get healthier.)
And if you find yourself thinking critical thoughts of yourself or anyone else, simply make a series or observations of what is right about that person or yourself. What is it that you (or that person) are doing that is good? What is a positive action you (they) do consistently?
Do this in threes, if you want.
Every time you feel less than great, simply give yourself a compliment. Keep complimenting yourself as needful until you get over it.
Every time you are critical about someone else, simply think something complimentary about them. Do this several times - not as penance, but because you want to personally get better (and help them as you can.)
Critical people are weaker and get sick more often. More often than they would if they went around noticing the positive attributes people have.
The human body is designed to live to around 150 years old. It's probable that little things like this could help us live to our potential.
Try it for yourself. Won't cost you anything. And it might even put a smile on your face.