Three things I've done for me:
1. Find or create a new challenge to focus my training on. It re-inspires me when I can get a chance to spar with someone who's way out of my league and then back off a little and get them to teach me...reminds me that I have so much more to learn. It's great when it's someone I don't regularly get to see...a guest. I find the same with forms and breaking. We need to feed that hunger to learn. Last time for me was sparring with a guest instructor with a very different style and techniques from mine.
2. Pick something to master and polish it. I think most of us have pet techniques, the ones that we know we do best. Again, my inspiration comes from watching others. When I see an insanely fast spin hook kick, a killer fast kick, or watch a national team master doing a form, I want to improve. I end up studying it, work on the mechanics, and find ways to polish it to a higher shine. Right now it's my kicking height. I'm trying to improve it in forms and work head level with as many different kicks as I can.
3. Play and be creative. The more time I spend helping with teaching the less I'm spending building my skills. It's fun, when I spar, to just try different techniques and combinations, not having to focus on the most efficient way to score or to make sure I don't embarrass myself. In practice with the kids, there are times we're working on one technique or sparring to win, but there are also times I want the kids to experiment, play, and just try something new. It doesn't always have to be what works. That fun factor helps let go of the pressure we take on as teachers. Lately (not with kids), I've been having fun with a twist on a game I learned in the service--two players spar until there's a clear point, then a third person enters on the side of the one who scored for 20 seconds. Light head contact is an important restriction. Change pairing and play again.