Holger Rune has a pretty clear idea as to what he deems a bigger achievement and it's definitely winning a Grand Slam as opposed to being No. 1 in the world.
Stefanos Tsitsipas explained a few times how he wants to be number one because it's the highest you can go. For him, that goal is even more important than winning a Grand Slam but for Rune, it's the opposite. The Danish rising star wants to be a Grand Slam champion before being number one.
Obviously, both are goals but the impact of being a Grand Slam champion is bigger according to Rune. There are some players that were never number one such as Goran Ivanisevic and Guillermo Villas but they won Grand Slams and they're remembered for that.
It's the first stat most people think of when it comes to tennis. How many majors have you won? Due to all that, Rune deems Grand Slam trophies and trophies in general as the most important thing for a tennis player.
Firstly, improvements, on my game, my physicality, because that's what I can control 100%. And then from there, probably the ranking. But it's more like, the team and the coaches. But me myself, I'm more motivated to win tournaments. I would rather win a Grand Slam and then be sixth in the world, than not win a Grand Slam and then be number one in the world. So for me it's about tournaments.
Being a Grand Slam champion will get you closer to being the best and it's been a longtime dream of his. For now, he's done well according to his own metrics. He has a few trophies, an ATP 1000 one but it's time to take the next step at Grand Slams. He's yet to do that.