I don't ever want to minimize practicing and doing the tedious learning, (that's important as well), but I have learned ten times more while "jamming" than I have doing anything else ...
I agree 100% (which doesn´t mean a lot)
I never had any guitar lessons, I´ve just bought a cheap guitar from a garage sale, rented a Beatles songbook, and let´s rock, Baby.
Admittedly, I never played the guitar on stage. I definitly miss proper lessons here, since I have no certain systems I can rely and fall back on.
Don´t forget, the most important thing is love.
(And I mean, girls. They just love a good jam)

Seriously, in my opinion, if you only want to write songs, it´s not necessarily wrong to learn to dance before you can walk, if you know what I mean.