What Leone said. Be willing to be a team player, even if that means your results for the match won't be great, it'll balance out in another match.
Had a match like that just a few hours ago in my King Crab on River city. Enemy did standard cluster around the citadel while we made an Assault (plus extras) push over the bridge. Enemy was distracted by the rest of our team who were keeping up the standard poke and fade facade you often see the team on the non-citadel side do.
We were coming through the airfield tunnel and the enemy was in a bad position. Our lead Atlas is discovered, don't know if he shot first or not but whatever the case, he flinched. He was taking damage and was trying to reverse instead of pushing through the exit. We were about to become the proverbial fish in the barrel.
So I shouldered past and stepped through the enemy fire, override on, weapons blazing like mad regardless of heat, twisting left and right. Already when I started the push I knew I wouldn't make it, and 2 more enemy mechs showing up confirmed that. I was actually surprised I managed to make it out of the tunnel and even into the cover of one of the buildings with the loss of only a side torso. Even got myself a kill versus a Shadowhawk. Then I died to a Kodiak.
But that didn't matter, because the rest of the group had followed in the push. Some through the tunnel, others from up high at the airfield and when they knew the reds were distracted by our push the rest of the team rushed the citadel from the other side and the red team went down in a withering crossfire.
I died early and had a pretty meh score, and it was glorious.
And as for what makes me personally a better mechwarrior? Patience. Not trying to be in front all the time regardless of what mech I'm driving. Taking the time to read the enemy team's actions (and just as important those of my own). Not commiting to a fight too soon. That makes me a better player.
Some of my worst games are from when I try to use MWO as an outlet to blow of some steam from work related stress or something. It's a game that lends itself poorly for such a thing.