If we inspect ourselves deeply, there could be a sin of rebellion lurking within. The anger could be because things are not working our way, the way we think, we desire or we want. We are unable to accept delays, postponements, failures, losses or negative outcomes even if we think are allowed by God for a better purpose.
There could also be a psychological condition of being suppressed in childhood or other sad events that has led to bottling up the anger. God understands you, therefore, one need not be very guilty, esp. if this not within one’s conscious control. **Repenting, nevertheless is a humble act of trust in God whenever you find yourself again and again falling into this condition **(any condition for that matter).
The remedy is to consider this as a part of our old carnal person that does not deserve any attention, but to be crucified with Christ. Instead, let us daily put on the new nature of the resurrected Christ (willfully) and focus on Him and his divine character! It’s an exchange, we give up our natural body (filled with lusts and passions) for the divine body of Christ (filled with grace and power). Read and meditate Gal. 2:20 and other similar passages.