How Far Can You Go To Save Your Relationship?

Having a rival to the point of thinking you'll loose your partner can be so disconcerting and can put you in an apprehension of fear especially when you love the person. So my question is this, how do you deal with a relationship rival whether or not it poses a threat to you?

People do so many things to protect their affairs, which include:
1. Fighting,
2. Abusing the rival on the phone
3. Involving security agents. 

4. Being the best you can in the relationship

How far can u go to save your relationship?