Here's the thing:
Life never gets less busy. The best time to find practice time is now. At every stage in your life, there will be plenty of things getting in the way of your practice time.
Allow me to propose a change to the mentality. Let's change "I should practice violin" to "If I really wanted to, I could practice violin." It's much more empowering. Change "I don't have time to practice violin today" to "If I practiced violin today, I would need to..."
Here are some possible endings to that sentence:
...wake up an hour earlier
...stay up an hour later
...watch my favorite television show streaming online instead of when it airs on tv
...not hang out with my friends as long
...set an alarm on my phone to remind me
...limit my time on the computer
...consider homeschooling instead of public school (an extreme, extreme example, I know, but there are families who do it, and specifically for the reason of getting really serious about violin)
...choose to limit my extracurricular activities
...plan out my homework assignments and projects well in advance so I'm not forced to cram
...fill in your truth here.
And, some days? You might not want to practice violin. You do need a day off now and then, for your physical and mental health. It's important to know that you're choosing those days, though. Choose a day to catch up with friends, go for a walk, clean your house, spend some time getting acquainted with yourself away from the violin. When you choose a day off, rather than it happening by accident, there's no guilt, and no shame.
So, what are you choosing for your violin practice today?