Beginners and, as a rule, self-taught guitarists forget about notes the moment they play them. As a result, they either go out by themselves or the fingers let go of them too early. This, obviously limits the quality of the sound. You think you played everything right, but it sounds mechanical, like a music box. I think we should dwell on this point a bit. This post is meant more for beginners, because to advanced players most of this should be obvious.
Most self-taught players only consider the beginning of a note. They would play a sound and immediately forget about it. What happens to that sound later, how long it's supposed to ring and whether or not it's even supposed to ring. In the end, the music becomes uneven, uncontrolled, with lots missing. Such playing has no depth, feeling, or the illusion of multiple instruments playing at once. This problem can be big and it can be small. It can also happen in only one voice or in all of them, but a beginner always has it.
This problem and a beginner's irresistible urge play as fast as humanly possible are directly related, because music, in their understanding, exists only in the moment of the playing of the note. They poke a fret, pluck a string, and yay music! After that moment, there is a kind of void, the expectation of the next sound. Obviously you have to pluck the string as fast as possible, so that the music doesn't stop :)
Actually, the music begins only after the note is played. Every sound has a birth, a life (development) and its going out. Three stages. Each of these three stages need to be controlled. A pause (silence) is also part of the music! and they all need to be sensible and under control, and not come out as mistakes or as disruptive to the melodic lines and voices.
It's very important to learn to listen to music from the very beginning. Make a sound and then listen to it. Pay attention to all three stages. One sound is one syllable of a musical sentence. Only then can you start adding a second sound to the first one. Now the goal is to connect these two sounds without a pause between them, so that one sound can smoothly transition to the second one. It's not as easy as it sounds. In working on this we develop our ability to listen. We come to the realization that a sound has a life-span. To connect two sounds is to say a first word. It is the first and most important step you will make as a musician. Without learning to say one word, you will never be able to communicate through music.
Then you have three notes, called a motif. After several notes you have a phrase. Then a sentence, and the sentences tell a story. Gradually we add more voices, and you can speak for 2, even 3, simultaneously. In addition, you still hear every word in each voice. You start to speak with meaning. This is what your goals should be.
But everything starts with one sound and the ability to hear it. After that, you can say your first word.