URF. Is it just me? Or...

So every time i play urf, WITHOUT FAIL, this happens to me. Is is just me or does this happen to everyone and i just don't know? So again like i said, sorry for reiterating, but this happens to me without fail. When I play URF I lose, even when I win my lane, lets say im top and i win, but bottom lane lost their lane. I will usually lose the game because the enemy lane that won lane (the losing lane on my team) will carry the rest of their team. Can anyone explain to me why this always happens without fail? is it because i cant carry hard enough?