Emotional stress is a tricky thing and often hard to overcome. It requires self-reflection and self-discipline; which are two things most people tend to avoid.
An example for a situation which causes a bit of emotional stress is when a parent grounds a child who has misbehaved. The parent empathizes with the child but sees the necessity for some kind punishment. Likewise, the child hates the punishment but regrets the misbehavior. Such a situation results in mild emotional stress for both participants, but through self-reflection both the parent and child can overcome it easily.
An example of a more difficult situation is when a person is in a love-hate relationship; let's say that the loved one has deep and endearing qualities but also at times prefers to treat people like shit. When to forgive and when to move on? Even if the person decides to move on, without self-reflection and emotional control the emotional stress will still linger on and affect behavior and health.
If you make a continuous effort to know yourself and make thought-out decisions, inner conflicts can be prevented and emotional stress is more likely to stay within healthy levels.