Too Much Repetition? Use Transitions!
If a piece of music is boring, it's probably because it repeats itself too much or in too many ways. If you look at modern piano music such as Phillip Glass, you'll see that they repeat-but-vary. They're not quite boring, they are just easy listening pieces. So while you may consider them repetitive, it is intentional... and I'm not a huge fan of repetition, ever.
Certainly these types of repetitive pieces work, but if you're like me you value variety and either a theme, some melody progression, or a key change throughout a piece of music.
The way to make a repetitive piece work as a "journey" for your listeners is by using transitions, and by building the overarching melodies directly from the transition itself. If your goal is to shift an A Major into an B Minor, you could use a short phrase (it could even be a massively important section) of music that will get you from A to B --- literally.
Other ways to eliminate repetition is to incorporate tempo changes such as ritardandos, accelerandos, and time changes. Changing tempo can change pacing, which can inspire new melodies in themselves. If you slowly progress from quarter notes to eighth note triplets to sixteenth notes (or in whatever way you decide to speed up) you may find that notes flow together in a different way then they used to and a new variation on the underlying theme you've been using.
There are plenty of ways to break the habit of repeating, and transitions are the best way. Start making a few phrases of strictly transitions, if you don't use them don't worry just consider them exercises. You'll get a hang of what a transition should sound like, and then you can get fancy and attempt to put elements of your melody in there as well.
These exercises won't help you if you don't have a strong grasp on melodies, however. You can't fix poor melodies with good transitions.
I would suggest taking a look at some repetitive songs with great transitions. This is a technique used especially in video game composing (especially Real-Time Strategy games like Starcrat, Warcraft, and Dawn of War) because it does not take away from the action in the forefront of the experience, but it changes slightly so that the listener does not get ear fatigue and annoyed with the background music. It sounds repetitive, so you will hopefully be able to identify with the repetition, but then it changes and you should also be able to identify the drastic changes as well.
This helped me when I was feeling boring and repetitive in my compositions. Hopefully it can help you too!