practice long structures
One of the trickiest things to learn when learning to compose is to gain a view and more importantly control over the big picture. It is fairly easy to learn and use all the “rules” and possibilities in small scale, having one chord and a melodic idea and finding a plausible way to a next chord with a plausible melodic idea. And while many learning composers very quickly get the hang of how this works, it takes a considerable amount of experience to also gain control over the larger structure. Many pieces by learning composers have very nice ideas in a small scale but in large scale hover over the same tonal center for minutes, have an unplausible melodic arc and lack climactic moments all together. However you can specifically practice “larger scale writing”. For example try writing a buildup that is for instance exactly 20 bars long (set a target beforehand!) and that gradually builds up for that time without taking away the climax too early or having an anticlimactic development somewhere in between. Or set a target to modulate in a plausible way within 9 bars for instance from Db major to G major. Write a symmetric melodic arc of 12 bars. etc. All these exercises will not necessarily end up with a presentable piece but they really force you to think in bigger structures.