Humans are literally hard-wired for external validation because we are a social species and we never existed in a vacuum. If you fucked up, or if you were weird, you were excluded from the tribe, and your genetic lineage died. Multiple this by millions of times over millions of years.
The people telling you to "love yourself first" and "seek self-approval inwards" are essentially telling you to gaslight yourself and isolate yourself so that their reproductive chances are better. The same goes for women who are told by therapists to go to movie theaters alone or go on walks because it's brave. It's a global competition strategy to make you more isolated and ergo less reproductively successful.
Sigma grindset males who tell you to work out for 2 years before you start dating, or just be as weird as possible, stop caring what others think, are literally trying to sabotage you so the dating market is easier for them. This is biological, instinctual and often subconscious.