There is a saying : " If you fail to plan, you plan to fail !".
Yaa, it's right to some extent ..
To me, the saying is not complete, let me add some touches to it ...
We need to have plan B or even plan C, apart from our master plan A, as a backup.
Backup or contingency plan can save a person from embarrassment and in some cases can prevent the person from being collapsed, either mentally or physically.
On another perspective, it's always appropriate to remain faithful to our significant other half without subscribing to this contingency practices :)