You're playing well and on a decent win streak. The games are hard as hell but you find a way to carry your team into solid victories. You win a few lose a few. Average day of league but you notice improvements you've made. It feels great because the fruits of your labor is paying off when YOU are the one putting in the effort to get better and it's showing through the numbers. All other factors being equal you will win be the one to come out on top.
Then your support is a filled jungler/mid lane main that wins about a third of his games. Picks leona and is incapable of making a single good decision all game. Flashed into the duo'd miss fortune alistar (with a 70% winrate and currently on a hot streak) at level 3 and gives first blood. You then get zoned off the creep wave for 12 minutes because god forbid you go for a melee creep without mf knocking out a quarter of your health bar.
Your top lane chogath gives a close second blood to kleptomancy nasus and proceeds to go 1/6 in lane.
Mid lane does ok but still can't quite compete against veigar that is getting support from kayn.
All the while your udyr gets executed not once, not twice, but 2 AND A HALF TIMES (invaded by kayn) dies 4 more times and afk's.
People complain about adc's getting powerspikes too early but honestly you have no control over the game until 15 minutes.