A Golden Rule of Practice

You learn much faster if you alternate between concepts and let them progress in parallel. It’s best to work on one thing at a time, but don’t wait for the one thing you’re working on now to be perfect before you work on something else.

For example, let's say you are a beginner learning a C major scale in open position for the first time.

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1. First you refresh your memory of the pattern each day without much concern for technique or timing. Just locate the notes.

2. Then spend a few minutes playing without the metronome, focusing on clean playing technique, damping the open strings so that only one note at a time is heard. It's ok if during this, you have to stop to remember where the notes are.

3. Then switch to building rhythmic accuracy and picking technique by playing a little bit faster with the metronome. It’s ok if during this last part, a few open strings ring out now and then.

The idea that one thing does not have to be perfect before you can study anything else applies to everything you can practice.

Another quick example: don't wait until you can play one song perfectly before starting to work on another one. If you did that, then after a year you'd only know one song, and that song would actually not sound as good as if you'd worked on 10 songs in the same time period.