Ake - my advice... don't get too strung up on the 'mechanics' of guitar playing technique...

My advice would be rather the opposite.

More importantly, keep your thoughts full of music, live with a musical soundtrack constantly in your head.

My advice would NOT be very opposite! ;-)

On the subject of classical technique... Classical music is not the be all & and end all, nor is good technique. But, to be brief ("Oh yes I can!"), there are many fine players of whatever instrument with poor technique. But better or good technique will always allow you to get closer to reaching your full potential. Again, whatever the skill. Poor technique inhibits what you can do, better technique gives you more freedom. If my memory serves, there was a chap here, a decade or so ago, who had questions about playing & singing guitar at the same time. My first question was about his posture. If you're hunched over your guitar, you're surely restricting your ribcage, and you'll either be singing into the floor, or cricking your neck back to look at / engage with your audience. All will affect your ability to sing.

And here's another more extreme one. One of my handful of teachers (yes I was willing to go & pay for lessons to improve) told me a story of a student (not sure if it was one of his) who kept passing out. It was eventually worked out that when she was concentrating hard, she held her breath... Yes, to THAT extent!

Utterly unaware of it, she'd keel over. Once she knew about it... I'm blessed by way of being VERY self-aware. I know where my arms & legs & fingers are (this is not so daft as it sounds - have a think about it next time you're playing); I know where I'm tense & where I'm not; I can watch someone else doing something & I will automatically attempt to copy them (don't ask me about the Tai Chi classes I briefly attended in my youth! :o ).

If you have the knack of self-awareness & of visual learning, it's a wonderful adjunct to any physical skill (total rubbish when it comes to cerebral skills; can't paint, draw, blah...). It's not that you should get strung up on the 'mechanics', as pfr puts it. But better technique absolutely DOES allow you more freedom to develop.

And, as I've already said, always have fun. Always allow yourself to giggle, or at least roll your eyes, at your latest cock-up. Reduces frustration levels no-end!