Do you train alone or do you have someone to train with? If you have always been a lone trainer, sometimes it's good to mix it up and have someone around. This is what a training partner is for. One of the purposes is to monitor your training, whether you are too slack or you are pushing yourself too much. Another purpose is to help keep you motivated which will then bring your workouts to another level.
This is the case for me and the mrs. I train her regularly and I know what she is capable of. As a trainer and a training partner, I remind her of technique and intensity while we train. And I must say it has paid off and she is enjoying the workouts. So, try to find someone to train with and you will realize that your training will be more fun yet challenging!