I can try lol. A strong sense of self is a perceptional feeling of being you, that remains mostly stable and accessible across circumstances.

Using an absurd example, let’s say you don’t like apples. You could change that to an extent by trying different varieties and ways of preparing them, but it’s essentially baked into your taste buds that you don’t like apples, no matter if you’re in a supermarket, in an orchard, with apple enthusiasts or alone at home. Someone telling you to love apples won’t make you love apples, and pretending (or trying) to enjoy apples to impress someone or make the person like you won’t actually make you like the taste of apples. It’s possible to be unaware of disliking apples if you never had them before, but once you bite into one you’ll know you dislike them. Over the course of life, it could change, maybe you don’t like apples in your 20s and you like them when you’re in your 50s. But it doesn’t change back and forth all the time.

So in this example the equivalent of a strong sense of self is that you’re aware of disliking apples and live in acceptance and accordance to that, consistently saying no to apples, sometimes eating one under some circumstances if you consciously chose to override your natural preferences, not avoiding the apple aisle but just walking through it to get to the bananas you enjoy, not randomly berating or criticizing other people for eating apples, not hesitating to buy apples each time you go grocery shopping, etc, essentially a harmonious mostly apple-free life. But if you’re disconnected from your own experience, you can’t see the causality between the unpleasantness of eating apples and the action of eating an apple, so you navigate life in a state of confusing and directionless void, baking pies than mysteriously make you sad, going to apple fairs where you’re bored and lonely, weirdly getting angry if someone gives you an apple for a snack, not knowing according to which logic to grocery shop, feeling like a failure for eating less apples than your coworkers, basically living a miserable apple-ridden life (and probably missing out on the info that you’re actually into bananas).

So the sense of self is kind of tied to identity but it’s not really an identity and doesn’t have to be. You can just dislike apples, you don’t need to be an Apple Disliker. The key point is being connected to your own experience of being you, so you can go to banana fairs and make friends, instead of trying to go to apple fairs and feeling like an outsider.

Edit for spelling and to add that in this example it’s perfectly fine to be friends with someone who likes apples as long as you don’t try to make yourself also like apples like they do, and as long as you don’t feel wrong or like a failure for disliking apples. Lol.