Daisy errr... Skye came into SHIELD as a newbie and to a certain HYDRA freak known as Ward, a weak girl. So Grant Ward met Skye as an inexperienced barely an agent not even knowing who she or her family is. He also vows to not hurt her. He does.
Lincoln Campbell meets Skye when she becomes inhuman and is there as she discovers who she is and there when she becomes Daisy Johnson. He is there when she hits her lowest point but fails to help her back from it. He sat he would never hurt her. He does that when he dies, dragging her even lower.
Throughout the next few seasons we have teases of potential romances for Daisy in the forms of Robbie and Deke. Robbie is more of a friend to her but he pulled her back but yet still hurt her. Deke, while he did have a one sided affection for her, he did cause her pain as well. He hurt her in different way by selling her to the kree leading to the beginning of the end for the team. Deke confesses his love for her but he only knows her as Daisy Johnson, Quake the superhero who has no flaws, never as Skye.
In season 5 we also see her get closure with some version of Ward. This version of Ward no longer sees her as Skye but as Daisy Johnson. Who somewhat understands that she is in love with someone else, ie Lincoln Campbell.
Fast forward to season 6, Daisy is moving on, wanting her "very own Fitz" aka in her eyes a soulmate. She turns down Deke for obvious reasons, hence him being the grandson of a woman she views as her sister. She is ready to dive back in to love.
With the team having to travel in time, Daisy must intercept Daniel Sousa, the first fallen agent of SHIELD. He is intrigued by her, not only by beauty but her intelligence. Upon joining the team, he spends all his time with her, always jumping in headfirst to help instead of leaving her to fend for herself like she is used to in some men. He saves her while others have been the cause of her pain. They carry that pain together. They pick each other back up. While never knowing her as Skye, he begins to bring out that innocence back all while helping her with her family and rediscovering herself once more. So when he says he would never hurt her, he means it.
TLDR;
Ward knew her as Skye, a vulnerable agent who carries the weight of the world on her shoulders. Causes pain
Lincoln knew her as Skye to Daisy, ake maturing into a woman. Causes pain
Robbie and Deke knew her as badass Daisy Johnson and didn't really see her past face value. Causes pain
And Sousa knows her as Daisy Johnson, someone who can be strong but yet understands her trauma. Carries her pain with her.
