If you mean, “I want this guitar RIGHT NOW!” You’re SOL. It’s all in priorities, and being patient. Delayed gratification is a good thing to learn.
Ask for money for the holidays, and bank it. If you get a tax refund check for working over the summer, bank it. Act as a designated driver at campus parties and charge for a ride, then bank it. Sell off stuff you don’t need.
Everything is about choices. You own the choice and the responsibility that goes with choosing. Every time you go to spend cash, think about whether or not you need to make the expenditure and bank the money. It’s amazing how fast it adds up, and how good the exercise of savings is for you.