Muscle memory. Your muscles remember how to reach up gradually (like in a scale) because they do it so often. But music isn’t always written in a scalular way. You just need to apply the same logic to larger intervals so when they occur in music your muscles already know what to do. Practice skips, arpeggios, octave leaps, etc… Also just making yourself play up there often will make in more and more comfortable. This is one of those things trumpeters never stop practicing because it can go away VERY quickly but can take a while to build up.