People with low self esteem tend to apply a different standard to themselves than they do to other people. Once we take those external expectations and we internalize them, it becomes a part of our identity. So if i start to believe that i have low self value, and i go and ask some one out and they say no, my mind uses that as greater evidence that i'm unlovable. It doesn't really do an objective analysis of like the reason they said no is because they've got terminal cancer and thy're going to die in four weeks.