The vast majority of successful pitchers are able to get three pitches over the plate - a fastball, change up, and breaking pitch (curveball, slider, etc.).
It is not easy to master three pitches, especially in this world of velocity as the single most desired metric - a sign of "validation" for pitchers. But the reality is that, in a game, your coach absolutely does not care about your velocity or how big and strong you are - just get the hitter anyway you can.
College prospects, if there are coaches coming to watch you, they likely know that you have a college level fastball - or a projectable one. When they come out to watch you compete in a game, they are looking at your secondary stuff. Think of it this way, an elite program wants elite secondary stuff, a lower-level college program is looking less intently at the quality of the secondary pitches.
It's up to you as to how far you want to take your pitching career.
Getting a quality breaking pitch is as much a mindset as anything else. Your thought should be, "I want the batter to swing at this curveball", rather than "gripping and ripping", hoping that you can make him swing and miss - there is a difference. Throwing with intent on the breaking pitch takes focus. Arm speed remains consistent, but ball speed must be at the absolutely precise speed - for you - in order to make it break into the strike zone.
How do you know what the precise breaking pitch speed is for you to be most effective in a game? There is a way to find out.
The next time you are in a bullpen with a coach or teammate, have them start taking readings on your pitches - the fastball velocity reading is not important, so don't try to throw it through the wall. If you are, for example, around 80 with your typical fastball, think about throwing these at 70 - just feel good.
When you are throwing the breaking pitch, either curveball or slider, do your best to consistently drop it into the strike zone for a strike. Do it a number of times and ask what the velocity reading is on each strike. You should find a range during that bullpen session which will help you know your best strike throwing speed.
Keep this range in your head, always.
If you are, say throwing strikes at 65mph, maybe a 66 then a 64mph, then you have a range and a feel in your mind of your best breaker. Here is the important part. When you get into the pressure of competition, this is the number or range you keep telling yourself.
"Keep this at 65mph"- not 75mph. Stay in control of your thoughts.
It may sound odd, but the biggest problems with secondary pitches come when pitchers overthrow under game pressure, causing curves to be erratic, or worse yet, hittable (i.e. hanging). So, keep telling yourself to keep it at the right speed!
By game time, you have prepared physically. That's why you train, to develop your specific skillset. Now, it is time to compete with your mind! Positive self-talk is one of the most critical skills that great pitchers possess. Prepare your mind with tools - like this curveball practice drill - to take into battle on the mound. In reality, you will probably throw your breaking pitches harder than you are thinking - intensity brings out adrenaline - your mindset will keep you in control of your pitches and prevent you from overthrowing when the lights are on!
This tip will help your coach see that you are a tough, cool competitor out there! There is no better label to have.