Time is, generally, a great healer. We can see it in everything. A cut finger heals, broken bones mends, as does a heart damaged in romance. Time does this. But it might not always heal if that injury took place and was repressed, or even deliberately suppressed. Post traumatic stress can rear itself from unconsciousness into intangible dreads, phobias, all manner of dis-ease (yes, delberately spelled that way) and in these instances Time is not a healer at all. So, as a generalization we can say the statement is correct. But when it gets down to particular cases, it is could often be not true at all.