"And become bright again." -- We, open-handed and rich in spirit, standing by the road like open wells with no intention to fend off anyone who feels like drawing from us -- we unfortunately do not know how to defend ourselves where we want to: we have no way of preventing people from darkening us: the time in which we live throws into us what is most time-bound; its dirty birds drop their filth into us; boys their gew-gaws; and exhausted wanderers who come to us to rest, their little and large miseries. But we shall do what we have always done: whatever one casts into us we take down into our depth -- for we are deep, we do not forget -- and become bright again
--Friedrich Nietzsche (trans. by Walter Kaufmann), The Gay Science
Kaufmann's footnote reads "A prose-poem like this should not be reduced to a single interpretation, but that is no reason for not offering even one reading"
I think it's about being tempted to resign one's self to what is ugly about life and to retreat into cynicism. Nietzsche, with this passage, stands in solidarity with these tempted ones and calls them to return to their most raw, natural, noble selves.