What could cause low quality sleep at night?

I woke up this morning with chest pain and a tired brain and usually I wake up refreshed and strong with plenty of energy. My theory is I did not consume enough yogurt or dairy the night before. I usually have multiple servings of yogurt and last night I only had one serving of yogurt, and I did not combine my yogurt with fruit before bed like I have done basically every day for the last several months. Its also possible my tiredness is due to dehydration that did not wake me up in time to refill my water.

What could cause low quality sleep at night?
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