First, Is not forbidden.

Marriage is based on Understandings, Tolerance, Care and also Adaptation.
If you can't adapt to situations it weakens the marriage and lead it straight to divorce,
If you can't tolerate your partner,it also leads same way. Same goes to Understanding. They all work together, if 1 is lacking and not fixed,it will surely end in divorce in time.

For a couple to reunite,they should be ready and agree to put all these in check, else is nearly impossible.