My professor asked me to practice the following on any string: index finger on fret 1, ring finger on fret 3, little finger on fret 5. I keep practicing but this is pretty painful and hard for me to achieve it. On the contrary, if instead of using the ring finger on fret 3, I use the middle finger on the same fret, then it becomes much easier.
Do you thing it is very important for a guitarist to keep practicing with the ring finger on fret 3 ? Or is it okay if I use instead middle finger ? Won't it get me into troubles later when I will want to learn complex positions on guitar?