I would say it all depends on the culture of your team. As a captain and ultimate junkie, I constantly look at the national rankings on usau, the power rankings on ultiworld, and some high level videos uploaded during the season, but take it with a grain of salt. We had the privilege of playing some of the top teams in the country this year too. When I look at the rankings, I also look at the film of the top teams, then the film of us playing some of those top teams. I think to myself, on our best day, if our execution is clicking on all cylinders, we can hang with these top teams. This is what you tell your team, not to show where they are as a team, but to set a goal for a level to attain as a team. Usually only a few people on the team look at these rankings like I do. The tough part is whether to announce the rankings to the rest of the team. But by this time, you spent a lot of time with your team. You should know how they react if they encounter good or bad. You can celebrate moments with team hangouts: bowling, parties, super smash bros tournaments, etc. It’s up to you and the culture.
Mental toughness starts on how you run your practice. Some teams don’t have the luxury of time (like mine), so they make conditioning a priority outside of practice. During practice we sometimes do some high cardio drills that don’t involve a disc: Serpentine, suicides, agility drills, etc. With little rest in between each rep, immediately move on to minis or normal scrimmaging. The focus is to play while exhausted and fatigued. After the scrimmage if there is time, possibly try to work on fundamental throwing drills. This practice can be done often in this order or even reverse, but it depends on your team structure.
For the member who resists change. Simple conversation involving the team leadership. The conversation should involve what direction they want the team to head towards. Ask if they are ready for the next stage. Respect their decision and try to make it come true. Next approach the member with high influence. Ask what vision does he have for this team. Does his views coincide with the leadership? Try to make sure everyone is on the same page. It all starts with communication, before action is made.
Sorry for the long answer. Hope it helped.