Ephesians 4:26 Be ye angry, and sin not: let not the sun go down upon your wrath:
It is not a sin to be angry. Anger is only an emotion, a feeling. Anger in and of itself does nothing external, outside your mind. Anger is a natural state. We will get angry. It is what you do about anger that is important. Do you let it stew until the pot boils over and you explode? Then you have sinned, you have allowed it to affect others.
We are encouraged to deal with anger, not to allow it to continue. I have found from experience that I get most angry about things that are not within my control. I have allowed frustration to become something more than it ought to be. Note the colon at the end of verse 26? Something completes this thought.
Ephesians 4:27 Neither give place to the devil.
Satan is like a fox that hears a wounded rabbit whimper, he comes a running. I don’t want to have to deal with Satan. I don’t need to hear his lies and I care not to be harassed by him. So anger should be dealt with as quickly as possible. Before the sun sets, meaning deal with it now. One other piece of good advice followed this verse in connection with anger.
Ephesians 4:29 Let no corrupt communication proceed out of your mouth, but that which is good to the use of edifying, that it may minister grace unto the hearers.
The last thing that your friends and brothers and sisters in Christ need is for us to fuel the frustration and anger that they share. Just because you agree with shared anger with a brother or sister does not mean that Christ is in agreement with you. Speak and pray peace over the issues. Let grace lead you to His will and perhaps His plans for you.
It is impossible to hear a still small voice while screaming.