Lesson 1 : phrasing
It helps the listener digest what you've got to say. It can also help you formulate exactly what you want to say.
Lesson 2: teaching yourself requires tolerance.
Your brain can imagine things long before your fingers can perform them, your fingers might hit a block and
it's your brains job to confidently and patiently find ways over or around that impediment: not to berate your fingers until they play it perfectly - that simply won't happen.
Lesson 3: Practice DOES NOT make perfect.
Only perfect practice makes perfect. If you play it too fast (that means at a speed you cannot consistently recreate) you're training your hands to make mistakes - each mistake will take 20-30 perfect practices to unlearn. If you practice something 10 times and each time you introduce a new mistake, you're looking at 20-30 perfect practices at a speed you can play at before you can consider turning the metronome up a notch.
Lesson 4: Easy does it.
Who's the better guitarist, the one who can play a hundred pop and rock songs or the one who's struggling to learn a few extremely technically challenging tunes? Who's got the better insight into basic musicianship? Good teaching is all about setting realistic goals - lots of small increments where success can be charted, or smaller steps identified.
When I read "I just cannot improve on the guitar" this thought occurred to me: you can't see how you've improved. Too ambitious a goal and you're only going to cross the finish line after a million tiny victories - but if you can't see those tiny victories, you'll lose heart long before the end is in sight.
Lesson 5: Familiarity DOES NOT breed contempt.
A lot of what people like about fast or complex music is the excitement, it can be for the person who played it first, but everyone who follows has the slog of learning how that first guy plays guitar as well as learning a piece of complex music, learning it is enlightening but is not the fast-paced adventure that listening to it was.
Lesson 6: Know thyself.
When you sit down to practice know exactly the goal you want to get from that 10 or 20 minutes, know yourself well enough to make that a realistic goal.
When you set out to play a tune, try and listen to your motivations for learning it; gaining admiration or acceptance from other people won't be strong enough motivation as they're vague and depend on other people doing what you want and you can't guarantee that.
Things like satisfaction at gaining a technique, having something you're confident enough to play in a band or open mic will work.
hope that helps
