There are two ways of treating cancer.
1] Treating it in its incipient stages.
2] Treating it after it spreads.
In the former case there is hope, in the latter it is MUCH more difficult to help.
In relationships there are problems. If they are treated early they are much more likely to be resolved. If one lets them fester, afterwards it may be too late.
This means that couples should often see someone [a Rabbi or Counselor] while engaged or early on in marriage when problems arise and they find that they are having difficulty resolving them on their own. Some couples wait too long and the damage is irreparable.