balancing that high-register guitar with those mid-register vocals

[natmj]

After recording for about two years, I think the hardest thing is to mix a high-register guitar solo that follows low-register vocals. Or any high-to-low or low-to-high register switch.

If you try to mix it evenly by keeping the volume at the same level, the low-register part is going to sound much quieter. But my worst fear recording is that I'll pull the vocals up too much higher than the guitar solo, and then the solo will sound weak compared to the vocals.

Is there any good way to do this or do you just get a feel for it after five years of recording?

I spent a lot of time on two songs in particular trying to get this right. I screwed up on one but did the other right. And I'm not sure why.

Thanks.