You pretty well miss the point of the questions... They are about self perception:
how you see yourself
how you think others see you
Your reply is very much about dealing with rejection, and perhaps imparting sagely wisdom while making sure you plugged your site. If only you had read the question! Lol
That aside, regarding your comment:
While I agree that indiduals offer opinions, from their perspective (as all opinions are), that does not automatically mean you should disregard their advice. An experienced person would be unlikely to offer something as simple and non-specific as "this song is bad". Indeed if someone does say that, they may as well say "Don't listen to me, I am venting".
Genuine consideration for reasoned opinions is a wise thing to do.
For example:
You are high in the Himalayas. You want to traverse across a gully. The other side is 30 feet away, but there is a 1000 foot drop between you and the other side. Luckily there are 4 snow bridges spanning the gap.
You pick one and prepare to cross. 3 other team members with your level of experience say encouraging things, and whoop with excitement. This boosts your confidence and makes you feel you have made the right choices. Your peers approve! Just wait until you cross the snow bridge and you can tell the world how right they thought you were.
Another climber of your level of experience says "You are a crap climber. You suck. Everything you do sucks." You and your gang are upset by this. You and your pals argue with him, and in the process become more determined to take the snow bridge you first selected, even though you are already giving it a second look. Being happy to have the support of the rest of your peers you celebrate by pushing the troublemaker off the edge and laughing as he falls, patting each other on the back. It's a win for team you!
Meanwhile, a more experienced climber says "I am not so sure. There are other options. Snow bridges are notoriously unreliable. Why not use the rope bridge the Sherpas put up last night? You just need to hook on and take advantage of their knowledge and skills." He points to the rope bridge, just a little further along "They don't care about being right, they just want you to cross safely". Noticing your reluctance at making a further effort, and seeing your steely-eyed determination to bask in the glory doled out by your adoring peers, he continues, "Or, if you are dead set on using a snow bridge, at least use a safety rope. I think your crazy, but it's up to you."
While you watch, a chunk falls off another snow bridge leaving it weaker, and then one almost identical to the one you plan to cross, collapses and falls into the crevice. The fourth snow bridge looks more substantial. You look at the three bridges left standing.
You look around your team and for a moment your eyes settle on your Sherpa. He's your guide. He grew up on these mountains and came from generations of climbers. He knows the environment like the back of his hand. Better. You raise a questioning brow and your Sherpa says simply:
"Snow bridge bad".
Do you:
Carry on and cross the selected snow bridge?
Cross the weaker snow bridge?
Cross the more substantial snow bridge?
Cross a snow bridge but using a safety rope?
Make the extra effort and cross the rope bridge?
It's life or death. Literally.
To disregard the Sherpa's comment is arrogance bordering on stupidity. Still, it is your life, your choice.
Even if the Sherpa had said nothing, the experienced climber has reasoned advice based on much more experience than you have. The snow bridge is still the snow bridge. The risk is still the same. A 1000 foot drop into strawberry jam like oblivion.
What do you do?
Back to the Music
Your music may not be literal life and death, but screwing it up can be damaging and wasteful. Does your music truly deserve less serious consideration? Do you value it so little?
Still your friends patted you on the back and told you it was good. That must mean something, right?
You are right, this is an industry of opinions. That does not make them all wrong.
What I would agree with is don't give up. Don't take rejection to heart.
What I think your lesson misses is that you should be prepared to learn from others, but not take what they say as definitive gospel. Challenge opinions and make decisions based on the various arguments for and against, taking account of who said what, and their experience.
Don't take comments personally. Indeed, if someone turns a comment about a song into a personal comment on you, that means they are too personally invested to be reliable.
Don't just listen. Learn to listen better.
If you are offering comment, don't make it personal. Step back. Keep your objectivity.
Alrighty, back to the original topic, self-perception....