Disclaimer: Please understand, what I'm about to say might step on some toes, but I mean nothing bad. Quite the opposite. I mean to motivate, and bear in mind I have a military background, thus I may come off a bit strong or harsh where I don't mean to. Again, no ill will intended.
When you queue up for a match, whether it's the first or the fifteenth of the day, come ready to win. Come focused. Come with a positive, ready attitude. There's no room for pessimism and doubt. There's no room for hesitation and holding back. And there's definitely no room for infighting. Whether premade or random, you're on a team, and you'd better act like it. Or you will lose. A lot. If you cannot do that, get out. Drop party and make room for a possible replacement that might have the right mindset.
Understand, you're not going to win every time. And sometimes in the face of your best efforts, the enemy's best efforts prove to be better. OR, in the face of your good strategy, you are met with pure brute force. Adapt. Overcome. And if you can't, then at least go down fighting. Cover each other, defend each other, work together. Teamwork truly is the key. And if you've never been on a team before, you are now. Fall in, and be ready to win.
There is no perfect strat. Sometimes you need to play it safe. Sometimes you have to take a risk. Hit that objective even if the enemy is already there. A few points you had to risk your neck for is better than none because you assumed you wouldn't make it. Assume nothing. The fight isn't over until it literally is. Flank, steal, lure, ambush, fall back, FIGHT. Winning isn't guaranteed, but giving up, holding back, or infighting practically guarantees failure.
But I say again, because it's THAT important: Come ready to win. Be positive, be focused. Last match was last match, win or lose. Be ready to win, or win again. You owe that to your team and yourself.