Sorry, but that's so simplistic and unrealistic.
We're not machines, that's the point. We're animals, social animals, so obviously the way others see us will affect our self-perception, unless we're megalomaniacal, and even then... Of course we'll take social norms into account, of course we'll give importance to all of that. We want to be loved and appreciated in a certain way, under certain conditions, based on our values and our experiences—values that depend on our experiences, and experiences that depend on our values. And besides, we're contradictory. It's not enough to think X to do X, it's not enough to be convinced by X to act according to X, because at the root of all this mess are our needs: the need to feel secure in our worth and usefulness within a group, to correspond to enough positive things based on our values, and so on. It's like telling someone with a phobia that all they need to do is understand it's irrational to stop being afraid, or telling a sad person that they just need to stop being sad. It's funny, but I see this a lot with men, some of them at least, the supposedly most "rational" ones. With their strong willpower and logic, they sincerely believe they control their feelings and emotions, and then the ego does the rest, creating cognitive dissonance, rationalization, and denial. It's quite a spectacle to see a jealous person vehemently insist that it's not the case, that something doesn't bother them at all, all while slamming the door. LMAO, we're so brainwashed by liberalism that we think we're all-powerful over everything, and all on our own, only to then feel like crap because, guess what, it's complicated. We're not all-powerful or logical, and it only makes things worse to not accept things as they are, especially emotions. They're facts; you have to accept them to understand them and understand why you feel them in order to hope to manage them.
I'm really tired of these oversimplifications that just make people feel guilty about their damn humanity and deny science itself.
Anon, take it for what it's worth, but the advice I'd give you is to identify the factors aggravating this feeling: your environment? The type of people you follow? The type of discourse? If it's about appearance, for example, constantly looking at beautiful people doesn't help. If it's a question of motivation, listening to stupid self-help speeches will make you feel more incapable than ever, etc.
Try to consider that not everything you feel comes from your thoughts. It sounds strange, but the cocktail of hormones at any given time influences your perception of reality, both positively and negatively. It could also be your external environment. Are there factors affecting your feelings that you can't control? Poverty, unemployment, trauma, where you live, access to mental health care, lack of friends? If you work through this guilt, things can only get better.
Nothing lasts forever. The worst times pass. Many people have overcome similar situations. You can't predict how things will turn out, so you're absolutely not condemned to stay in your current situation. In fact, the opposite is unlikely. Try to cultivate as much curiosity as possible about the future, about who you will become, and how you will perceive yourself.
Imagine yourself from an outsider's perspective, like a friend. How would you judge yourself? Are you sure you're not being too hard on yourself? Unfair, even?
If you're feeling really bad, tell yourself you're in the worst possible state to trust your own judgment. Seriously.
The more you find moments of joy, the more you'll feel entitled to judge those negative judgments, whether they come from you or others. The better you feel, the more freedom you have to choose which opinions to consider, which people you value enough to let your perspective partly depend on you and on things. The better things will get, the more you'll trust your ability to question others' views and have the final say.
Hold on to what makes you feel good. Don't underestimate the little things. Details aren't small for everyone. Your small victories aren't small. What makes an action easy or mundane depends on how difficult it is for the person. If you're depressed and taking a shower is wonderful, then rejoice in that shower. Congratulate yourself even if you don't know when you'll have the strength to shower again. The better you feel, the more your brain chemistry will shift, and you won't see things, including yourself, in such a negative light.
Take care of yourself, please. Support ♡
If you can, find help and, above all, talk. It's impossible for you to be alone in what you're feeling.