I've felt burnt out as a designer quite a few times in my life. It's been best described to me as a loss of control over your outcomes. A lot of us are suffering from similar experiences. If you are one of them, I hope these ideas help.
- Take control of the little things
When I was younger I used to detest chores (I mean who likes them?). As I've grown older I've found it rewarding to take ownership over my surroundings. Taking time to prepare your environments (if you don't already) will give you a sense of both accomplishment and control over your life.
- Design your environments
Once you've taken control over the minutia in your life, I've found that applying some of your design skills to your immediate surroundings can help a lot. Designing a wardrobe, a room, a desk setup. I don't mean going out and spending a lot, but finding small ways to improve your work from home or office.
- Take ownership
One problem I see many designers face over the years is not taking accountability and ownership over the outcomes of their work. Look back at your projects for ways to improve. Look ahead on new project and take ownership from the start. Take complete ownership, I think you'll find the work more rewarding.