I feel like what she's saying is that, with every disappointed love, those feelings become increasingly rare. Our hearts become tougher, to withstand abuse, but the downside of not feeling as much pain is not feeling as much in general. She remembers when she was a teenager, and every experience with love was pure and consuming, and even when we've grown beyond our teenage years, sometimes that feeling returns, and it's just like being in high school again. Meanwhile, everyone around her is buckling under pressure to get married to the next acceptable option, so she takes comfort in the words of her friend, who would rather be alone than settle.
I feel like what she's saying is that, with every disappointed love, those feelings become increasingly rare. Our hearts become tougher, to withstand abuse, but the downside of not feeling as much pain is not feeling as much in general. She remembers when she was a teenager, and every experience with love was pure and consuming, and even when we've grown beyond our teenage years, sometimes that feeling returns, and it's just like being in high school again. Meanwhile, everyone around her is buckling under pressure to get married to the next acceptable option, so she takes comfort in the words of her friend, who would rather be alone than settle.