WASHINGTON (WASHINGTON POST) - A bouquet of red and purple flowers sat on the front porch when Bailey Sellers got home from lunch with friends.

With it was a note: "You will be receiving this until your 21st. Love, Dad." Sellers had just turned 17.

Then came pink flowers for her 18th birthday; red for her 19th; pink and white for her 20th; and finally, different shades of purple for her 21st.

Purple is the color symbolising awareness for pancreatic cancer, the illness that killed Michael Sellers on Aug 25, 2013, three months before his daughter's 17th birthday.

But Michael Sellers had planned ahead, pre-ordering different arrangements from a local flower shop in Maryville, Tennessee, for his youngest daughter's birthday until she turned 21. He wrote different notes for each arrangement.

"He wanted to make sure that she knew that she was loved, and that he would be there through every milestone," his widow, Kristi Sellers, told The Washington Post. "He wanted to make sure that she understood that he was there."

Bailey Sellers celebrated her 21st birthday on Sunday (Nov 26). With the bouquet was a card decorated with colourful butterflies, a bittersweet and final goodbye from a father to "his most precious jewel."

My dad passed away when I was 16 from cancer and before he died he pre payed flowers so i could receive them every year on my birthday. Well this is my 21st birthday flowers and the last. Miss you so much daddy. 💜 pic.twitter.com/vSafKyB2uO — Bailey Sellers (@SellersBailey) November 24, 2017

"This is my last love letter to you until we meet again. I do not want you to shed another tear for me my Baby girl for I am in a better place . . . I will still be with you through every milestone, just look around and there I will be," he wrote to her one last time.

As she's done in the past, Bailey Sellers shared a picture of the bouquet on social media. She also posted the note and a photo of her in a bathing suit, sitting on her father's shoulder."This year, I expected 10 likes just like I did every year," she told The Post.

To her surprise, her story resonated with hundreds of thousands on social media."I woke up one morning with my phone completely frozen," she said. "It's crazy . . . I have no idea, I have no idea how it went viral."

Michael Sellers had two other children from a previous marriage, a son and a daughter. He gained a stepdaughter when he married Kristi in 1994. Bailey Sellers, born two years later, was their only child together and the youngest of the four children. "He loved all of them," Kristi Sellers said, "but she was the baby."

Bailey and her father bonded over sports. He coached her basketball team from when she was 4 to when she was 15. They often practiced at the gym or in the driveway of their home in Maryville, just outside of Knoxville, Tennessee, Kristi Sellers said."They just literally could not spend a day without one another," she said.

In 2012, Bailey's basketball team won the national championship. She said she remembers seeing her father jumping in excitement after her teammate shot the winning basket."It was the cutest thing I've ever seen from an old man," she said. "He screamed and ran to the center of everybody and picked me up."

Something unusual happened to Michael Sellers later that year: He slept all day on Christmas Day, something he'd never done during his favourite holiday. Bailey Sellers said his stomach hurt so badly that he just tried to sleep the pain away.

Michael Sellers was diagnosed with Stage 4 pancreatic cancer in early 2013. Doctors told him he had only two weeks to live, but he could prolong his life by a month with chemotherapy. He opted not to have the treatment and lived for another six months, Bailey Sellers said.

She still vividly remembers the day her father died. Michael Sellers had been in a coma for two weeks. His wife was sitting beside him on the bed, talking to him."It's okay, it's okay," Bailey Sellers recalled her mother telling her father. Then, her mother asked him if he was "sad because of Bailey."

Bailey Sellers said she watched in awe as her unconscious father shook his head, a tear dropped from his closed eye and down his cheek. Michael Sellers died that night.

A month before he died, he asked his family to buy handkerchiefs and to have them embroidered. Alone in his bedroom, he prayed over every single one of them and later gave one to each of his three daughters. He asked them to tie the handkerchiefs to the wedding bouquet they would one day carry as they walked down the aisle, Kelli Sellers said.

"He was just an amazing father, an amazing partner," Kelli Sellers said. "And he supported his family through all the bad times." One of those bad times involved Bailey.

When she was 12, she was diagnosed with Ehlers-Danlos Syndrome, a genetic disorder that affects connective tissues, mainly the skin, joints and blood vessels. Sellers said her body is in constant pain and the joints in her hip, shoulders and knees dislocate at least once a day."I pretty much lived in a hospital my entire life," she said.

One of the worst hospital visits was after a kidney failure. Doctors sent her to a hospital in Cincinnati for surgery. Only she and her mother made the 322-kilometre drive because her father was unable to get time off work.

Lying groggily in a hospital bed after an hours-long surgery, she saw her father, carrying a bouquet of flowers."You didn't expect me to miss this, did you?" she said, recalling her father's words.

Bailey Sellers is now a junior at East Tennessee State University, where she's studying psychology.

After her father died, she had her right wrist tattooed with one of the notes he'd written her, inked on her skin to resemble his handwriting."I will be watching over you from Heaven."