Many clients I have worked with over the years that have been training alone or with a personal trainer and seeing very limited results have missed a key connection with training, nutrition, and their goals.

Your training style should match your goals. 

Your eating should match your goals. 

Your training style should match your nutritional intake. And vice versa. 

Now there are many many ways to adjust these to all align. But think of these examples. 

If your goal is weight loss. Nutritionally you need to be in a calorie deficit. Training sessions should be created to assist in creating the best/biggest calorie deficit (within reason). 

If your goal is changing body composition. Nutritionally you need to prioritize protein, carbs, and fats correctly. Training sessions should be created to make the most adaptations to the muscular system. 

If your goal is to be stronger and faster. Nutritionally you need to be in a protein surplus, calorie surplus (possibly), and balancing macronutrients. Training sessions should be created focusing on central nervous system training and increasing neuromuscular signaling. 

If your goal is to be stronger. But nutritionally you are in a calorie deficit and limiting fats and proteins. Then your training sessions focus on creating a calorie deficit. These are not aligned and those strength gains will be painfully slow. 

When trying to achieve these goals make sure you know the differences or find someone that can explain them to you.