Happy birthday !!! and I did your chart a few minutes after your birth time so I hope this is right!
Mars is usually the key to Anger, especially if there are hard aspects to say, Mercury (argumentative) or Pluto (more violent).
Looking at your chart you don't have either of these - but you do have Mars in Scorpio - a sign that it rules, which gives some passion and intensity to the way in which you assert yourself and Mars is trine to your Pisces Sun - this is quite a positive contact but Pisceans are idealistic and Mars in Scorpio is passionate assertion so you might well find yourself getting 'angry' in situations where you feel that ideals need to be asserted - in some cause of protection of some group, person or animal that you think is suffering. Your Sun is in the sixth House a house of service to others - so you may well go in for causes.
In your case this is reinforced by a very tight semi-square from Jupiter - you will fight for your beliefs - no two ways about it - Jupiter is the planet of expansion and growth, Mars of assertion so you will assert yourself in a big way if necessary. The semi-square is a challenging aspect so you may well find it difficult to channel the assertion constructively - leading to anger. Indeed this might be quite a problem but Mars is in a loose conjunction with Saturn which adds some ballast. Mars/Saturn links either result is a fear of fighting or caution about fighting on the one hand or a desire to be authoratative and dominant on the other.
Mars is on the cusp of your third house of communication and 'thinking', which lies in Scorpio, so Mars also rules this house - which suggests that you might well express yourself forcefully, given the above. It also rules your seventh House of partnerships so you need to be careful with your relationships!
Jupiter is in your fourth house of family - so they too may witness your anger.
Now, overall you are not an angry person being a Water/Earth mix, so most people are likely to be surprised when you do get angry - probably including yourself!