Switch it up.

Do cardio, weights/toning, core or whichever is in your regiment on different days. Not only does it break up the usual, but you will actually feel the difference and you are working on everything.

I hate weights preferring cardio and more fast paced exercises but because it is challenging, I feel it the next day. My body gets out of the rut and I actually feel the burn.

Music, making it fun and having ideal goals/inspiration is what really does it. Make it something to look forward to to jam out and play.