I practice guitar. have practiced on and off for about 2 years. well i bought the guitar 2 years ago. and I reallay haven't practiced that much. But i have practiced enough so that I'm good at playing melodies. But

-Chords, i just can't do them. They hurt too much and i get sprained . I dont want permanent damage so i just don't practice that much. I already have permanently damaged thumb and finger from doing office work so I just don't wanna risk it more.

-Playing scales fast and trying to get faster. trying to practice for speed. --Well i practice everyday just alittlbit but many times, even though i have already been playing for 2 years, many times i get sudden aweful pains in the fingertips and it stings so bad.. then for about 1 day it stings so much i can't touch nothing. Moreover, if i practice too much i get carpal tunnel syndrome symptoms really bad because i already suffer from that. So that's why i don't really play much.

Anyways, so my question is.can anyone Just become  great by Practicing lots and lots like Tommmy does, or like that other autralian kid "Smoking Joe" plays?...I don't think anyone can just practice alot and become great. Some people may have stronger hands and fingers  OR may risk their health but I wouldn't want to risk it alot. So i'm probably never gonna get good enough.