Doing the same things over and over and going through similar processes can be boring even on Instagram, which seems pretty fun as everywhere else. Keeping the same theme over and over can also get boring over time.
In this case, the first thing to do is to find a theme that you really have fun preparing and enjoy playing with colors. For example, if you feel happier playing with dark, moody tones, use that theme. The key here is to enjoy.
What you can do when you're really bored is to create a transition period. This transition period can be three posts or six posts at will. The differences you make during this transition period can lead you to new ideas and at least you tried new things. Also, if at the end of the day you find that you want to revert to your old theme, you can easily revert from the transition grid.