Are you mixing your workouts? Are you doing so with a specific purpose in mind, or just blindly picking and choosing? The truth is many people (and trainers alike) just want to ‘change it up’ without any thought into why any one exercise or drill was chosen.
With my background, I look at this issue from the perspective of Systema training. If you want results and if you want to achieve a level of mastery, you need to start with understanding and learn the ABCs. Once you understand the alphabet of a system, you need learn fluency in applying the basics to everything. Too many students get to high levels and think that it's time to start cross training.
So wrong …
Far too many people obsessively debate which system is best. I don't think it matters which system you master first because systems are artificial. Only experience is real. Systems are only delivery platforms for experience. Ultimately all systems lead to the same point. All the masters I have worked with tend to do similar things, move in similar ways, and say similar things.
The most important advice that I could give to someone just starting out is to choose a system that you enjoy in your heart. A system that resonates with you will allow you to confront and overcome the challenges you are facing.