Is this dangerous? Is there anything else before I continue?

I have the hardest time waking up every morning no matter how early I sleep the night before. So what I do is put one caffeine pill next to my bed so the next morning I can take it and help myself wake up. I'm 17 and I would like to know if its safe to keep doing this, if not what are the major negative effects? To be honest, after taking this (I started maybe a week ago) my mood's been a lot better and I'm definitely a lot more vigilant at school.