The only time I would ever make this statement is if I actually won the Most Diligent, Intelligent and Focused Undergraduate Student Award.
You didn't include the rest of your statement, but it's hard for me to believe that an undergraduate outcome has the capacity to demonstrate these three qualities. Course marks or a cGPA are hardly an indicator of diligence or focus, and certainly not a marker of intelligence the way I would define it.
I find that the best statements don't so much state the personal characteristics of the applicant in so direct a way (a la the conclusions of a lab experiment) but relate how these personal characteristics are demonstrated in real life. The reader is not so much TOLD that you are diligent, intelligent and focused as much as he or she UNDERSTANDS that you are these things.
If you really, truly wanted to include this statement, I wouldn't position it in the end. I would start somewhere at the beginning:
My peers have remarked that my most endearing qualities are my diligence, focus and intelligence. During field experiments in my final year, we spent 17 weeks in Borneo tracking a potential new species of shrew. Our equipment broke down by the second week and we were suffering from malarial fever by the third week. I jury-rigged a camera trap made from vines and the bottom of a coke bottle and stayed in a single position for 14 weeks. My perseverance paid off when I captured short (2-second), grainy footage of the animal. By then, my entire team had long since abandoned me. I thought they were weak.