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A concluding sentence should restate the topic, and supporting evidence all within one sentence. Your final paragraph itself does an excellent job at restating the main idea with evidence so this was kinda difficult. I'd go with something like "Santiago never gave up, he persevered through his tough time, just as we should through our tough times." I'd go with a sentence more or less like this because it states the main topic of perseverance and never giving up, while also giving evidence by clearly saying Santiago had also went through a time and never gave up. Feel free to add more to the sentence, just be wary of making it a run-on sentence.