Try this exercise and see how you cope
Using the notes of a C scale play it up to the octave and back down at the 8th fret on the E string.
C D E F G A B C B A G F E D C
On the first play you give each note 8 counts
Second play you play each note 4counts
Third play you play each note two counts
Fourth play you play each notes one count
The idea is to play it altogether as one flowing exercise.
What you will find is that using the 8 count playing each 8 note times is easy moving through the first part.
Even the second part of playing each note 4 times is easy.
But now the dexterity starts to increase, not the speed...you are still playing at the same tempo, but the dexterity between both hands has become more interconnected so the brain will get in the way, you may find yourself tripping over notes and so in effect lose time.
There is no physical reason for this, the tempo is the same, the speed of the notes are the same, but the dexterity of the two hands working together has changed.....there seems less and less time to settle on a playing tempo.
All that is happening is your brain is feeling rushed because the fingers on the fretting hand are becoming more involved in the playing.
Again this could be taken as playing faster, but the tempo is still the same, all that has happened is the tempo is being sub-divided different so it may seem faster, but in reality it is just more dexterity.
It is like the old riddle of what weighs more.. a ton of feathers or a ton of coal?
The answer to both is understand what is being asked and then address it with the correct answer. If you do the above exercise at 80 BPM, then as you work through to the single note part it does not get faster as it is still and always will be 80 BPM, it just seems that way because it gets more dexterous....it is the brains perception that it is faster rather than dexterous.
So when you can play this exercise through the 8, 4, 2 & 1 smoothly, then learn to play through 8, 4, 2, 1, 2, 4, 8 so you develop the feel for counting rather than actually physically doing it or have the metronome define it's every beat.
The principal of the exercise can be developed to other scales, Arps, triads etc
I use the children's song Twinkle Twinkle Little Star to demonstrate the idea when playing music.
If you know the song, simply play every note in the melody as a half note in a given tempo. It will still sound like the song even though the note values are wrong.
Then again using the same idea now play it using quarter notes , this time it will sound closer to the original arrangement because the note values are in the main the same as the song.
Now play it again using 8th notes, then develop it again to 16ths if you can, but no need to develop 16ths, just by trying it it will reinforce the idea that the tempo will still be the same although it sounds faster...you should realise that even though the dexterity of playing gets more each time and the fingers move faster, the tempo does not increase, the song does not get faster....the tempo remains consistent.
This has more to do with getting the brain involved in understanding tempo so when you start to count and sub-divide you hear and feel a steady pulse (a tempo ) rather than one that is on every beat. Once the brain understands the job and relates it to the playing it becomes a sub-conscious....it happen as a matter or course.
Like riding a bike at the start is all about balance and motion working together, once you have the balance,the motion develops because of it. You never ever have to think about your balance again, only where the motion is taken you.
So for your metronome once you learn and play a song to its click, simply half the click so you have more time between them....then half it again to create more time etc.
Again, just because there is less time between clicks in relation to the tempo does not mean you play slower, and as such when note values start to get shorter or longer you are playing them in tempo in relation to whatever click you have in your head, and that click in your head needs to be developed by understanding your relation to tempo and how you will represent it in your playing.
