Switching disciplines can be exciting and beneficial for both you and your horse. This doesn't mean that you'll have to switch disciplines forever, but trying one new thing each month is a great way to test yourself as a rider.
I began riding hunter jumpers when I was very young and it wasn't until the end of high school that I ever even sat in a western saddle. I would occasionally be allowed to go to the local polo fields and warm up one of the polo ponies, but for some reason I always stuck to riding hunter jumpers. It wasn't until I helped a family with their naughty horse that I really began riding western. Now I ride primarily western but make sure that I switch it up every once in a while by riding bareback, english, jumping, trail riding, running around a few barrels and even playing polocrosse with friends. Since I've been trying new things the horse that I ride (Wilson) is much happier than when he's in his normal routine of strictly arena work and being ridden western.
Set a goal of trying one new thing each month with your horse!
(Make sure that when you are trying something new that an adult or trainer is there to walk you though it and make sure you are safe)