A question I'm often asked by students is, "how much should I practice?". My simple answer is the more effort you put into it, the more you'll get out of it, but I'll go beyond my generic answer to explain a bit more. Music is not unlike sports where the athlete improves his or her skills through repetition  known as muscle memory. Muscle memory is the simple act of repetition (get used to that word) and eventually knowing something so well that your hands know where to go without having to consciously thinking about it. 

So, how much should you practice? In an perfect world, I recommend practicing at least a half hour or more per day. I realize with busy schedules that this is easier said than done. The point I'd like to emphasize is to practice as much as you can, even if you have to do multiple short practice sessions. Practicing a little bit on Monday and then a few minutes on Saturday is going to slow down your learning progress. If you wait days after a lesson to practice, it will be harder to retain skills and techniques taught in the lesson.

What if you're getting frustrated? There's a 100% chance that at some point that you will get frustrated. I've never seen a student who hasn't, myself included. My best advice is to take a break from the piece and practice something you already know well to ease your frustration.

Only practice when you can give your undivided attention to your instrument. This means putting your smart phone away and turning off the TV. Practicing means practicing the lesson you were given and not just noodling on your instrument. I encourage noodling and experimentation, just don't let it define you practice sessions.

A note to stringed instrument players: Guitar and stringed instruments are physically demanding and you may feel some discomfort as the calluses on your fingers develop and your finger muscles get stronger. If you postpone practicing because your fingers are tender, this will delay callus development and prolong your discomfort.

The legendary cellist Pablo Casals was asked why he continued to practice at age 90. "I think I'm making progress" he replied. 
Woodstock School Of Music