When a player is trying to make a team, increase velocity, or gain power to crack a starting lineup, there is that little bit pressure deep inside. It manifests itself differently in each person.
Some guys shrug their shoulders if they aren't seeing increases each time out (poor body language). Others find an excuse or blame something other than themselves (poor mindset). Don't be discouraged if you hit a personal best one week, then, next time out you are back down. This is very normal. It is an "up and down" path.
Many factors come into play when working to be the best you can be. First, your human, and that means the mind and body get tired at times. The old saying, "the mind is willing, but the body is weak", is a good way to think about those days when you may feel like you should be showing big improvement but just can't make it happen - it is normal.
My advice? Get your workout in, get out of there, go home, reset for the next workout. That is the baseball mentality at its core. This game is a challenge when you are feeling 100%, let alone when you might be distracted or tired.
I had an interesting conversation with a college coach, who, when recruiting, has an interesting metric that he looks at when looking for the perfect fit for his program. He investigates the players academics - like most coaches - but he puts extra weight on class grades and attendance each day over test and exam scores. We all know of kids who are not the best "test takers" but get good grades because they come to each class on time, do their homework, and participate in class discussions. In other words, they ask questions.
You aren't learning if you aren't asking questions.
So, this particular college baseball coach prefers the players who go to class (practice), ask the teacher (coach) questions, and is sure do their homework (practice on their own), over the player who "thinks they know all of the answers" and plays hard in games only (test time).
There is an argument to be made for each type but think about the grind of a baseball season. It takes attention to routine more than the ups and downs of an occasional game with some practices in between. Don't get me wrong, a great talent who is able to produce when the lights are on will likely not be turned away in the beginning, but, over time those "shooting stars" will either lose their positive influence on the team or adjust to the grind and become a better person and player.