This was tweeted by a man who was a college football player and who is now the sales manager of a large corporation. It sorta fits his background, wouldn't you say?
There is every reason to encourage people to have "the right mental attitude." That can help take one far. However, taken literally, and many people take this sort of platitude literally, it means that if you've succeeded in life, it must be because you have "the right mental attitude" and if you've been unable to overcome adversity, it must mean that you have "the wrong mental attitude."
I'm cruel to say this but if the person who wrote this comes down with cancer, his "right mental attitude" may not enable him to achieve any goal he may have. If medical treatment doesn't work, he's going to suffer and die. Whether medical treatment works has almost nothing to do with his "mental attitude." Whatever goals he may have had will not be achieved. If his son or daughter develops schizophrenia, having "right mental attitude" won't get them very far. They'll probably be unable to work on a regular basis, regardless of their mental attitude. Life circumstances can completely overwhelm any "mental attitude" no matter how "right" it may be.
I deal with clients every day who feel that their disability isn't so much caused by their illnesses as by their personal shortcomings. They feel that being out of work means that they have failed even though objectively they haven't failed; they're simply dealing with serious illness. It's bad enough to be sick. It's worse to mistakenly think that your inability to work means is your fault when it isn't.
As a society, we're eager to tout the successes of those who have overcome disability with the "right mental attitude" while ignoring the fact that the disability overcome seldom involves factors such as chronic severe pain or chronic progressive illness or chronic severe mental illness. We like nice stories about people in wheelchairs who are still working. We think that's how we'll be if illness strikes us. We'll have the "right mental attitude" and be able to overcome our disability. When we hear stories about people with bipolar disorder who end up homeless, we want to think that can't happen to us because, unlike the homeless people, we have the "right mental attitude." We don't want to consider the possibility that the difference between the person in the wheelchair who is still working and the homeless person with bipolar disorder is the nature and severity of the disability rather than "mental attitude." We think we can control our "mental attitude." We don't like to think about the fact that we can't control illness and injury.
Writ large, this is the problem with this country's attitudes towards disability. We think that people can control disability with the "right mental attitude" but that's a delusion that leads us to be cruel to disabled people and even to ourselves when we become disabled.