I’m not certain what any of these tattoos mean because Harry has never confirmed it. But my best guess is that he divides his body into dual negative/positive statements that represent certain sentiments for him when he is otherwise unable to express those sentiments.
I believe the general idea comes from the Serenity Prayer that discusses things one can change and things one can’t change in life: “God, grant me the serenity to accept the things I cannot change, courage to change the things I can, and wisdom to know the difference.”
Therefore, with these tattoos, Harry seems to STRONGLY delineate that there are things he feels he can change or deal with in his life, and things he feels he cannot change or endure.
For example, when Zayn was expecting a baby girl in early 2020, Harry showed up one day (after a while of hiding and ceasing all promotion for Fine Line and press interaction) with the green/gold cross combination removed from his necklace. And suddenly he was wearing a single pink shoelace on the side of “Things I Can’t, No, & Non” part of his body, seeming to express a negative reaction to the baby news.