The speech I couldn't give due to my dad's death

Elbie Seibert and his parents pose in April, shortly before his father's death.

Elbie Seibert is the 2019 valedictorian at Columbia High School in Nampa, Idaho. He will attend Brown University in the fall on a full-ride scholarship as a QuestBridge, Jack Kent Cooke, Horatio Alger, and Sidney E. Frank Scholar. The views expressed in this commentary are his own. View more opinion on CNN.

(CNN)To the graduating Class of 2019,

I want to begin by saying thank you. Many of you -- particularly those in my hometown of Nampa, Idaho -- have been so kind to me over the last few months. And, Lord knows, I could not have weathered the storm without you.
Though I am not able to give the speech I intended to at my own high school graduation -- on account of my father's recent death -- I wanted to share with my fellow graduating seniors four major lessons that this last year has taught me. They've given me some clarity, and maybe even a little peace, and hopefully they can do the same for you.
Elbie Seibert
First, never take anyone or anything for granted. The day after Thanksgiving last year, my family received devastating news -- my father was diagnosed with metastatic bladder cancer. I had exactly six months and five days with him before the disease claimed his life. And since his death, there isn't a second that goes by in which I don't think about the time I could have spent with him -- watching him yell at the movie screen after an exhilarating Hitchcock thriller, listening to him sing along to every Whitney Houston hit, smelling the aroma of his delicious chicken Parmesan cooking in the oven and just generally basking in his love for the world.
    Even the sadder memories -- like helping with my father's catheter after he no longer could walk or holding his hand while he struggled to speak -- are ones I will cherish, as they remind me of a time when he was still here with me.
    It's been a week since he died, and my body aches from missing him so much. But, and I know you're about to think, 'Oh, how cliché,' I also know that he will always be with me. I can feel him in my bones, hear him in my dreams, see him in my shadows -- and I find some small comfort in all of that.
    No relationship is ever perfect -- and even my father and I had our ups and downs -- but I ask you all to never take any of them for granted. You never know when they will be taken away from you, and even when you do, the pain that follows still deeply hurts.
    Elbie Seibert and his father pose for a photo on Thanksgiving, one day before his father's cancer diagnosis.
    Second, never ignore the warning signs. Shortly after my father's diagnosis, he told me that he had been urinating blood for over a month but was forced to ignore it because he could not afford a doctor's visit. As a janitor with a family, he struggled to pay for his employer's health care plan and did not have sufficient coverage for his needs. Now, he's gone, and my family will live with that cost for the rest of our lives.
    I know it's easy to ignore the warning signs -- especially when acknowledging them carries a high price tag. But whether you are struggling with a health issue, reflecting on an abusive relationship or considering the coercive yet dangerous actions of your peers, I ask you to never ignore the warning signs -- it could cost you your life or the life of a loved one.
    Third, never stop fighting for what you believe in. If the costs of dealing with warning signs pose too great of a challenge, I encourage you to fight against the systems -- or injustices -- that make addressing them so difficult. In my father's case, it was an issue of unaffordable health care costs. As I prepare to move across to country and begin the next stage of my life, I hope to use my education at Brown University to better equip me to fight for a country where health care is accessible for all Americans -- no matter their financial background or employment status.
    While I may never get to hear my father laugh again or see him hug my mother, I will commit to fighting for a society where the cost of a doctor's visit does not mean forgoing dinner or running water -- a situation that my father has had to face numerous times.
    It can often seem as if one voice is never enough to drive change, but with the collection of individual voices comes a powerful call to action. So, please, when you see something broken in society, dare to stand up and fix it, whether it be through advocating for progressive legislation, attending protests and rallies or volunteering for an interest group or political campaign. Your voice does matter, and it can make a difference.
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    And, finally, never let where you come from stop you from dreaming. If you look at my family, you might say, "This kid never had a chance." My mother is a loving homemaker but she suffers from cerebral palsy and is limited in her ability to move around by herself. My father was a janitor before his diagnosis -- and we lived a very modest lifestyle.
    Yet I never saw my circumstances as forms of adversity. Instead, I embraced them as essential elements that helped shape me into the man I am today. As the son of a diligent janitor and differently abled mother, I would have never thought that I would become the first student from Columbia High to ever attend an Ivy League institution, and yet I am proud to announce that this has become my reality. As the recipient of a full-ride scholarship, I want to encourage all of you to remember that nothing is ever impossible, no matter how difficult your circumstances may be.
      Although my situation may be unique, we all have overcome challenges to get to where we are, and that is something worth celebrating. And remember -- the challenges don't define us; how we respond to them does.
      Congratulations, Class of 2019! Go out and make some waves in the world.