Asked mainly because

Conservatives say that's one of the things they believe in

It often seems to be wrong or misused ("if everyone just used masks and stayed home the pandemic would have ended long ago") ("not using masks during a pandemic has consequences for other people and thus doesn't belong in personal freedom")

A definition for stuff that fits the question could be this:

• The credit or blame for consistently failing or succeding at it is largely on you

• While you can ask for advice to get better, you have to do it yourself

So the main examples that come to my mind are largely (well) personal:

• Being motivated and committed to work towards what you want

• Being hygienic

• Being good at socializing and figuring out what's your relationship with other people gonna be

• (although obviously, given socializing depends on other people, this is very dependent on them doing the same and accepting/recognizing you or your choices and so is more accurate on progressive or apolitical social environments)

Which is good but doesn't explain it being used as a political belief.