I've had Tom Clancy's Rainbow Six Siege for a couple years now, and I really love and enjoy the game quite a bit. My roommate recently picked it up as well and is on the rise playing the game almost everyday with his mind set on getting his rank up; as a result of this, I wanted to write a little bit about how our perspectives differ and why I think that is.
Personally, I tend to be a more casual player; especially when it comes to First Person Shooters. I'm not super competitive with them, but I really enjoy playing them. The fast-paced, action filled environment with a tactical and information-collecting focus is extremely entertaining to me and is something I find very enjoyable. While I definitely may be frustrated when I get killed in an embarrassing fashion, or when I actively knew an enemy's position but they still managed to kill me, I overall am pretty good about keeping my composure when playing the game.
On the other hand, my roommate who recently started playing is much more competitive. He's very much concerned about his rank, and gets frustrated by any minor mistake he may make whereas I shrug most minor things off even if it costs me in an encounter. He wants to be able to do better and outperform other players on the game even though he's newer to it, and is much less casual about his approach to the point that he actively avoids playing in "Quick Match" for fun. It's a much different take and perspective than I have, but I can understand the thrill of competition and being able to prove yourself over others. He is much more careful about how he picks operators, considering his team composition and what would be most beneficial given the map he is on, and is even more considerate of what his team requests of him since he is a newer player. As a result of this, he defers to appeasing his team and trying to help them as much as possible since he knows he will definitely serve as more of a support character earlier on in his pursuit of become a well-performing ranked player.
I generally do not consider these things, as when I open up the game my main intention is to have fun more than it is to win. Sometimes I'll even play "Recruit", which is an operator without any specialized gadget and is generally not something that is played unless one is quite literally trying to "meme" on another player. Other times I'll play Tachanka, which is an operator with an automatic turret that is generally considered poor in performance but can be very fun to play. Another thing that is frowned upon is "spawn rushing", which is where you at the start of a defense run outside of the building you're defending to attack the attacking team as they spawn. It is a high risk, high reward thing to do as after 2 seconds your position is revealed to the enemy team, but it can let you pick off a number of players very early on in a round. All in all, these kinds of things are usually moves pulled by people who don't care about winning a match, as they're unnecessary risks and picks that can cause problems for your team but are notably very enjoyable to the player.