Critical thinking is making sure we have GOOD reasons for our beliefs.
Critical thinking is checking for assumptions – our own and other peoples – critiquing assumptions, and challenging them if they are found to be lacking in sufficient and necessary evidence to be considered true. Sufficient and necessary evidence IS good evidence.
Not all assumptions and claims are equal, however. Good evidence is not good enough when the claim is extraordinary. Extraordinary claims require extraordinary evidence!
Personally, I want to believe only those things that are true. If I find out that something I believe is not true, I will no longer believe it. For me to believe something I must have sufficient and necessary evidence (‘good’ evidence*) that it is true. If it is apparent that it is not true, I won’t believe it. If there is not sufficient and necessary evidence either way I will sit with not knowing – and that’s okay.