You have to train your left hand - if you are right handed and perhaps your right hand if you are left handed – to move fast and with memory. This training can only be attained with diligent practice.
Be patient with yourself while learning. If you feel like your hand might need some rest when you are practicing, then go take a rest. If you are stressed or nervous, then try some other time, maybe the next day when you feel more calm and relaxed.
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It is best to practice for short periods of time, say 20 minutes at a time. This prevents you from being frustrated and learning the guitar will actually be fun. It will be something that you will look forward to.
It is best to leave your guitar in sight and out of the case because every time you see it, you will want to pick it up. In time you'll understand that learning how to play guitar is a continuous process. There will always be new techniques to practice and new tricks to use.

One of the first decisions you need to make is what kind of music you want to play. This may seem obvious but it's strange just how many people start to learn to play without finding the right teacher. If you start learning with a teacher who prefers classical and that is what all their training is about and you are actually interested in playing Jazz, you may lose interest and give up.
For beginners there always is the question of whether reading music for guitar necessary or not? The truth is that it really depends on the player themselves and what their final goals are. For a classical player hoping to make a career from their playing then I would advise them to start studying music notation - for everyone else it isn't necessary.
Don't waste your time trying to play music you hate. Learning how to play should be a challenge but the process should also be fun. It is still vital for guitar beginners to start learning some music since that is what it is all about and being able to play some tunes encourages people to work harder to learn more.