Keep in mind that shipping new features & products to customers is the only thing that matters. Code quality is just important to keep up the pace and make sure that we can always keep going forward. This is not an end goal. No customer will ever thanks you for your code but will always praise your good shit.
Always put the team first. Helping a teammate always comes before your own schedule. We go forward as a team, no need to sprint alone if others can not follow your steps.
Always value others' work. Cheer your teammates up, help them reaching the next level.
And remember: leave your ego at home, the team don't need it.
Being a team player also means giving blood, sweat and tears to help the team. Don't sit on the bench waiting for others to do the job. Be involved, be on the playground, play your game at your best, give your best to the team.
1 pixel of non-alignment is 1 pixel too much.
It's ok not to be perfect, it's not ok to know that it's not perfect. Do not ship badly crafted features. Your craft must be perfect at least in your own eyes.
Forget about back or front. Being a team of fullstack developers is beneficial for multiple reasons:
big individual impact by being able to deliver a whole story, back to front, end-to-end
more likely to be able to fix any bug
common understanding and greater respect for each other
smaller dependency to one's individual skills. We can all take over one's work.
In a nutshell, being a fullstack developer will give you freedom and responsibility.