My internal dialogue depends on the day, on some days it is kind and considerate while on other days there are no censors. Above all what I’ve come to notice is whatever the mode is, I guess the kind, considerate and forgiving attitude is the nicest of them all.
We often are the toughest to ourselves. We say to ourselves things we would not say to strangers or friends.
Guy Winch has awesome TED talk about this emotional first aid. Favoritism over body over our minds. I.e. we do not take the wounds of the mind as seriously as we should.
In essence our psychological health requires as much attention and routines as does our physical. One of the best routines for our minds is what Ajahn Brahm calls kindfulness, combination of kindness and mindfulness. Being aware of our thoughts and then have the courage to have compassionate, considerate attitude towards those thoughts.