Things that didn't make since/ Biggest noob mistakes you made when you joined?

1.)For me, it didn't make sense at all that deals magic damage.... using knives. i would go full armor tank then gasp in disbelief that kat popped me. 2.) i would use global ultimates while aiming with the mini map 3.) i would always rush regardless of my matchup 4.) i rushed every time i ADC'd because it gave attack speed and ms

Anyone have mistakes they often made when they started or things that just didn't make sense to you?