Be angry and do not sin; do not let the sun go down on your anger, and give no opportunity to the devil. (ESV – Read the chapter)
This is a verse that is often misunderstood and misapplied. For starters, Paul is not somehow outlawing anger here. Sometimes believers let themselves be convinced that negative emotions of any kind are not appropriate for believers to experience. This is far from the truth. A quick look at the Scriptures reveals this to be the case rather conclusively. Our God is a passionate God who experiences a full range of emotions. Jesus in particular experienced loss, hurt, anger, rejection, and so on.
Negative emotions are not a problem for believers. What we do with them is the key. If we let them overwhelm us and become our filter for engaging with the world around us, this is not good. If, instead, we make sure they are fundamentally righteous in their origination and orientation, and use them to drive us to seek the plans of God with ever greater focus and intention, they can be a very good thing.
Because of sin, there are situations in which anger is the appropriate response. In fact, in these cases, to not get angry is a bigger problem than getting angry is. Sin should make us angry. It should make us angry enough to want to do something about the problem. Our anger over sin should propel us to righteousness. This is good anger. Anger is not a problem. Sinning when we are angry is.
The other part here that is misapplied is this notion that we should not let the sun go down on our anger. The fact is, some brushes with sin leave us with an anger that isn’t going to be gone in a few hours. Paul’s point here is not that we need to some how resolve every problem at a sitcom-like pace, but rather that we should not hold onto our anger any longer than is absolutely necessary. When anger is the right response, we should be angry. But we should immediately begin to working to resolve the cause of our anger so that we can move on to other emotions that are better suited to the kingdom of God.
When we hold onto our anger too long, we do indeed give the devil a foothold. The longer we remain angry, the greater and longer lasting will the temptation be to do something sinful in and with our anger. When we do this, we will have created another problem that will lead someone else to be rightly angry, starting a whole cycle of anger that doesn’t benefit anyone but the devil.
So go ahead and be angry when the situations demands it. But, turn your anger over to God and let Him be your guide in the midst of it. He will show you first whether or not it is righteous anger or merely self-righteous anger. He will then guide you to do something constructive with it so that you can move past it. By this, you will be right on track with what Paul is encouraging here.