Written inside Kasey Mitchell’s yearbook is a quote from Houston Texans defensive end J.J. Watt: “Success isn’t owned. It’s leased, and rent is due every day.”

From a young age, the midfielder for the Mount Sinai girls’ lacrosse team was living by those words.

Mitchell first played lacrosse when she was in second grade, on the boys’ team at Comsewogue.

“It definitely helped me grow as a player,” she said. “I was a lot smaller than everyone else, but my dad wouldn’t let me back down to any boys. He still doesn’t.”

She joined the Mount Sinai girls’ varsity team in seventh grade, and was originally brought up as an attack.

“She was always a kid that was destined for greatness,” Mount Sinai head coach Al Bertolone said. “She was tough. Earlier on, she was just a confident attacker. I often feel that if she hadn’t torn her ACL in her freshman year, we probably would’ve gotten upstate [to the state championship] one more time. But every year she’s played, she’s done better and better — leading up to her finest year this year.”

Mitchell suffered her injury during a junior varsity basketball game, and came back three months later, competing on the lacrosse field in the county championship, where the Mustangs lost to Shoreham-Wading River.

During that healing period, her father, Pete, who is also the boys’ varsity head coach at Comsewogue, installed turf in the backyard to be able to practice with his daughter.

“When she tore her ACL, I made a commitment to train her,” Pete Mitchell said. “It’s kind of amazing that she ended up being the player that she is. She works hard every single day and there’s no substitute for hard work.”

He said his daughter’s commitment from a young age, much like the quote she lives by, contributed to her becoming an important piece of the Mustangs’ puzzle that helped the team achieve greatness.

“She was a tough kid — very athletic, and she worked real hard,” he said. “She loved the game and she was always around the boys, always around my team, and she got a good sense of the game and I think that’s one of her biggest assets. Her lacrosse IQ is very good. She goes to the gym every day, she has a personal trainer, and all those things and her successes have been a dream come true considering where she came from and how hard she’s worked to come back from her injury.”

During Kasey Mitchell’s sophomore year, the Mustangs went 20-0 overall and claimed the school’s first-ever Class C state title. In her junior year, the team went 18-1 overall with an undefeated, 14-0 mark in Division II. Mount Sinai made it to the Suffolk County Class C final, where the team lost to Bayport-Blue Point, 11-9.

Bertolone said the coaches sat her down at the end of that season to go over her individual and team goals, and to come up with a plan that could help her achieve them. The solution was moving her to midfield.

“When it comes to talking about Kasey, it’s just her evolution,” Bertolone said. “She was always a very, very good lacrosse player and her skills of course got better over the course of time. This year we moved her to the midfield and she was good on both sides of the field — offensively and defensively. She doesn’t care where she plays as long as she plays. Sometimes you’ll have to put your personal goals aside for team goals and she did that.”

She finished above 75 percent on draw controls, and scored 75 points off of 57 goals and 18 assists for a Mustangs team that went 20-1 overall en route to its second state title.

Besides her contributions to help win games, Bertolone said she was thankful for all Mitchell was able to do as a team captain.

“She was more like a coach on the field, and has great leadership skills in all facets,” he said. “She took care of business on the field and she took care of business off the field. She was really nurturing to the younger players; she was one of those quintessential senior leaders this year. She was outstanding.”

These contributions on and off the field earned her All-American honors — the major goal she had set for herself and Bertolone worked to help her achieve before she heads off to play women’s lacrosse at Stony Brook University. She was also named All-Tri-State and All-Long Island among other accolades.

“Lacrosse is what I grew up doing and since seventh grade lacrosse has been my life, day in and day out,” Mitchell said. “Bertolone is like my second dad, he’s helped me be the person I’ve become and without Mount Sinai lacrosse I wouldn’t be where I am today.”

A main reason why Mitchell said she chose Stony Brook is because despite her injury, head coach Joe Spallina was still interested in having Mitchell be a part of the program.

“After my ACL surgery, I was a little slow and kind of limped, and while a lot of colleges didn’t look at me, he never gave up on me,” she said. “Spallina didn’t hesitate to contact me and recruit me, so that was one thing I really appreciated about him.”

And she’s excited to see not only what she can do for the program, but what Spallina can do for her.

“He doesn’t doubt people — he’s completely turned around a couple of athletes,” Mitchell said. “I’m really excited to see what he can help me do and accomplish. Ever since I was a little kid lacrosse has been my entire life and I love playing it. There’s not a day that I don’t play it, honestly, and to just have the opportunity to play at such a high level with such a great team that has a great coach and great teammates … I just can’t wait. It’s a dream come true and I’m honored to be privileged enough to play at Stony Brook.”