MODES, and getting to "know" them in the biblical sense.
Learn the legally acceptable chord forms of the modes (I know, we don't play chords!) since they set up the form of the boxes that give one confidence in playing an upper neck note.
I also like how the bass increases confidence in the guitar and vice-versa. I have also imagine playing a kazoo would help too. Every instrument you add just opens more and more musical doors.
But truly, for me this is how it worked when I broke down and finally learned the MAJOR MODES, which then opened up the minor modes (i, ii, iii, iv, v, vi and vii). I was a decent street player, but when I finally "got" the MODES under my belt, the upper neck was no longer forbidden territory.
Work on the I, IV, and V modes first and not surprisingly the II, III, VI and the MYSTERIOUS and dreaded VII MODE will be your newest BFs. It ain't REALLY work if it makes you smile.... which you will.......smile, that is!
The I, IV and V MODES will fit about 85% of CW, Rock, Blues and also give you tremendous insight into Classical and Jazz, not to forget any Strauss Waltzes you may want to play.
Not sure about Polka though. (jk ..... or maybe not!)