It's been my experience with 30 years of coaching young people that it's the coaches job to build confidence and create ownership on the part of the athlete. Whether they perform well or not in practice or in competition, they own it. This doesn't happen right away as there needs to be a trust relationship that can take a couple years to develop through good communication. It's a process that takes time as the athlete matures and processes information, watches positive and negative role models and decides what they want from the experience. The coaches role is to guide responsibly, explain "the why", support with data that shows rate of improvements, work with the athlete where they are at, etc... Being negative is a sign of a coach that is ego driven and coach centered rather than athlete centered. As mentioned earlier, getting to know people outside of athletics is a major part of developing trust including letting them see you are human as well.
It's generally expected that when there are large numbers on a team, there's a division of levels of interest. There's always the group that cares and will try hard no matter their age or talent level. Then the group that might be involved for social reasons first but figure out how to be competitive with themselves and others at their level with encouragement. Then the group that has a lot of other interests and are running to stay active, maybe their parents are making them do it but they are compliant. Then finally, the kids that really don't want to be there, don't try and take short cuts trying to drag others down with them. They are quickly identified and strongly encouraged to pursue other interests. They self eliminate, no need to get upset about them or give them any more attention than they deserve or earn. The rest of the team is glad when they go away even though they are a minority but easily recognized by their peers for what they are. No different than in the classroom.
Talking to young people like adults brings them further along at a quicker rate. You get better results sooner. Holding them back early and focusing on the championship season performances when they are ready to physically, mentally and emotionally ready to turn it all loose has always worked for me. The trick is bringing them along at the rate they are ready for in all three categories so they are able and motivated to take ownership of where they are and willing to take an educated risk they deem appropriate without regrets.
I've never stepped to the starting line for any of my athletes but I remember what it was like and what would have worked best for me if I had my ideal coach. As a result, I have a large number of former athletes that have continued competing well after high school and have chosen teaching and coaching as a profession. That is what I am most proud of.