Since their highly anticipated, and brilliantly delivered, warm reunion, in last season's opener (No Sanctuary), these two had tons to catch up on, after weeks of separation--Carol's exile from the prison--and then governor psycho's army blowing holes into the prison walls, rendering everyone else homeless, then separated. Carol soon regrouped with Tyrese; who had the girls, while Daryl had escaped on-foot with young Beth--surviving on the open road against strayed walkers, while seeking temporary shelter--and any slim hope that the others had also survived.
Following their much anticipated, and openly welcomed reunion, situations had definitely altered within their relationship. Beforehand, Daryl was the one holding back and often confrontational, due many unsettled emotional demons, from his abusive childhood and an overbearing, obnoxious older brother (Merle). Now it was Carol who faced the inner demons, via the brutal loss of three young daughters, from differing circumstances, and a murder accusation from Rick; though the situation was clearly a mercy-kill. It was now Daryl's turn to keep Carol close, and prevent her from shutting down--attempting to leave the group, over false or misdirected guilt and shame.
Taking night watch together, Daryl silently and patiently awaited Carol to open up about their lapsed time--and Karen's death, and the two little missing girls. But Carol was not ready to discuss it. Nor if she ever would. The reality was far too painful--especially after recovering from the devastating loss of her precious young Sophia, nearly two years earlier. Carol had long learned to shove dark feelings and emotions out of her system, and remain focused on duties and survival--in their often brutal, very changed world. And Daryl understood her silence--where he had been, countless times. Carol's close presence was satisfactory. Daryl could keep a protective eye on his woman; not that she'd needed it nor required it. The lone wolf knew that the bad-ass lady warrior was perfectly capable of defending herself. Heck, she'd boldly rescued them all from the clutches of Terminus--blowing the place to near shrapnel.
After Daryl spotted the getaway car that had kidnapped young Beth, weeks earlier--Carol joined him on a high-speed chase into the outskirts of Atlanta, ending up at the back door of a women's shelter; which Carol recognized, the moment they'd stepped inside. Daryl instantly realized what was going on inside Carol, and refused to let her shut down again; remaining close by. They were best friends, and understood each other. Daryl knows Carol's being and she knows his. Every next maneuver Carol attempted--needlessly downing a nearby walker, or packing a book about surviving abuse, into her duffel bag--Daryl was right there to reverse her actions--signaling that she didn't need to "prove" herself anymore--that she had the strength of ten men, and the beauty of all women.
They've known each other long enough, to have developed a best-friend bond-- requiring mutual trust, respect, and embedded love for each other. They became soul-mates--which truly exceeded their original friendship; developed over time, through Carol's patience and understanding of Daryl's history, person and temperament. Both victims of abuse and dysfunctional homes--they had lots in common, including a silent, but obvious mutual attraction. Daryl realized his feels for Carol, during Season 3, after she went missing in the tombs; presumed dead. He privately grieved her loss...Then later, found her (barely) alive, and then carried her back to safety.
A man of few words, Daryl openly expresses his obvious feels and care for lovely Carol, through body language or actions. Thus, Carol became comfortable with teasing Daryl--on a regular basis--even calling him 'Pookie' at one point. And Daryl has learned to lighten up and realize that the group--and Carol--were his real family--and that he loved and respected each one, differently. Carol patiently taught Daryl about real love, respect, family, and honor. And Daryl eventually opened his heart and soul to her--about everything. Outside of Rick--He could trust Carol.
Then the attempted rescue of young Beth Greene, had met the girl with an unexpected, unfortunate death--and Daryl, once again, shut down emotionally. After all, he'd spent several weeks alone, on the open road with the girl; after losing the prison. It was just the two of them, and they had to accept each others company if they were going to share a temporary shelter. Eventually the two had put aside their personal differences and became friends. Daryl began to realize that he was equally guilty of judging someone before actually getting to know them; having been in such disposition, since he could remember. However, he had never judged Carol, and soon realized that he could not simply judge a naive girl, simply because she'd lived a sheltered life, before the world turned.
As Daryl shutdown, over the loss of Beth, Carol knew what to do and what to say to him. She always has. No one, not even Rick, knows the warrior wolf, better than Carol Peletier. Her precious, unforgettable kiss on his forehead, was reminder to Daryl, of their unbreakable bond, and that they were always there, and together, no matter what. Their obvious bond has survived all of the odds; duly tossed carelessly and carefree, at the entire group--and has proven that best friends (and potential future lovers) are never truly parted.
As we look forward to what Season 6 brings The Walking Dead, we can be rest-assured that Caryl was developed for a reason. Two individuals, with lots in common, in spite different backgrounds--were united under like circumstances--realizing that they were not so very different. One half; struggling to heal from his inner demons, and accept "outsiders" as his new family--and a special woman who would soon become his best friend. The other--happily widowed, and a free-bird, able live her own survival, and become part of a real family unit again--and truly love a good man, worthy of honor.