It definitely matters. You can't make progress if you don't take it seriously. People plug away and make some serious errors along their journey and then wonder (sincerely) why they have not made any progress. I'm here to tell you that attitude and approach are the key. They definitely matter.
We've all seen this person at the gym. They come in with a matching outfit. They look really cool. They do a set of chest presses on the Hammer machine and then start talking to anyone around them who will listen. They begin discussing the baseball game from the previous day. They talk about the latest sports rumors. They talk about anything anyone will listen to. They do this to avoid having to work hard and feel the pain.
The chatter is cheating themself. They are spending time, time that can never be recovered, doing nothing at all to further their goals (if they even bothered to make goals in the first place). In addition, they can destroy you if you are not careful. Avoid these people at all costs. Do not engage with them. Stick to your workout and get out of the gym as usual. Let the chatter take themself off course.
The Pickup Artist
This is the person who is only at the gym to find a date. They lurk around staring at members of the opposite sex like they are part of a buffet line. They fail to adhere to any strict plan because their only interest is in getting a date. While the gym is a great place to meet like-minded people, it is not the place to solely for the purpose of getting a date. The pickup artist is doing themselves a disservice as they are, again, wasting time that can never be recovered. You need to avoid this person. If you want to meet them, wait outside the gym after your training is done and get their number for a later conversation, but don't let them ruin your time in the gym.
The Easy Does It
This one drives me the most crazy. This is the person who does everything with a weight that is so light their newborn child could lift it. They seem to be at the gym for the sole purpose of passing time. They do not want to push themselves and they do the same workout over and over again. This is pure insanity. This one won't really get in your way. If they annoy you, don't let it really get to you. Just remember that they are going to look the same (or worse) next year.