Ummm, PRACTICE! Old joke, but still funny.
Practicing isn’t the same as playing. Of course you’re always “playing”. But to practice is to focus on a problem and try different avenues to solve that problem. Playing is when you’re just enjoying the music, playing an entire piece. It’s what happens after you practice.
Effective practice requires a plan and a goal- what are you going to work on. What do you want to achieve. You need to have a setting with all your tools- metronome, pencil, music, rosin, instrument, and closed door. It is quite annoying to be working on a shift, or a measure of “bow only” only to be interrupted by an inquisitive pet or ringing phone. Once you’re in the “zone” you can accomplish a great deal.
I set a timer (thanks, Alexa) for each item I’m going to work on. Usually 20 minutes for something really tough that requires intense focus. Difficult measures that require slow, methodical finger choreography. I like to play my orchestra music along with a real orchestra, so I have recordings in my Amazing Slow Downer and I can play along with these (at a tempo I can play). But this only comes after I have located the problem areas (faster, complicated runs) and spent my 20 minutes on those.
You need to find out what works for you. I like to keep a spread sheet of what I’m working on, what measures in each piece need extra attention. It helps me remember what I need to do. Make your plan, set some goals, and go practice. Every little bit is another step up that mountain.