"If I has known it would be a beautiful and sunny day I wouldn't have sleeped that much". This is something I always think when I have free time and I spend it sleeping. For me, to sleep it's just a waste of time but the problem is that probably i'll have this thinking again. So if someone asks me what I regret, i'll say I regret of wasting my time sleeping. But let's be honest, don't waste our time sleeping is very hard.