Not always the case, sometimes it's flat-out onesided. The loss that set off my recent 11-game losing streak featured my high-bronze/low-silver teammates against three Golds, a Platinum and an unranked 30. I was the only one my team with a kill, 3/8 as Kayle against a Plat 5 Kassadin.
Back on topic, things happen in games and it's out of your control. You're in Bronze 4 now, you have plenty of time to hone your skills in games where people give a damn. Find a champ to take you out of Bronze (when I get ranked, it'll probably be Akali for me), whether it be Teemo, Aatrox, Ashe. Once you get good, you'll win more than you lose with them. Ride that train as far as you can, but make sure you have a backup plan (ex. if you get stuck at support and Thresh is banned).
Ex. I like having five champs at each position, to prepare for three getting banned and the fourth taken by someone else.
At top, I like to roll Garen, Teemo, Shen, Elise and Gangplank.
In the jungle, I like Jax, Zac, Aatrox, Nocturne and MUNDO.
My mid laners are Akali, Kayle, Lux, Master Yi and Ezreal.
AD carries of choice are Vayne, Jinx, Corki, Sivir and Quinn.
Supports are Taric, Thresh, Ashe, Karma and Morgana.