I Have a Question

any ideas of why my internet would work all day and then quit at 6 or 7 at night and how to stop it from doing that? I had this happen on fri and sat this wk and have no idea why, it does disconnect sometimes but its usually no big deal and i just connect again, but this wknd once it quit it quit and there was nothing i could do to get it going again. i got lucky today and it didnt do that. and yes, century link is going to check it out on wed for me but in the meantime i was curious what caused it and what i can do to stop it. any suggestions?