I'm suffering with the same thing too. I'm 20 years old and since I was 13 or even younger, I contained my anger all the time even today because of the past, because how I was treated, this and that. Not to mention I'm depressed as heck.
Honestly...
Theres no quick way to fix this. It will take so much time.
For me, when i was sick of this poision, this hatful side of me- I went to church, met a nice Christian lady- my elementary school teacher, she sat with me we sang hymns together. The preacher told us to sit in a group and just talk to each other. With how we felt, what are problems were, what we were thinking.
The lady talked with me about my life instead of hers, I told her about my problems with certain people, how sad I was with my brother who hated me for so long, anything that I've kept to myself.
And then I cried. She hugged me and cried with me. That was the first time in my life that I let out some of my sorrow, anger, pain- in front of a living person.
Afterwards, I felt alive when I was walking home. I felt like I was going back to being a normal, loving person. I talked with my dad which surprised him. I felt love and loved...prolly coz I was saved at that time. 2017.
So, the best way to get rid of some or ALL of your bitterness, hatred, etc. Is by SHARING and telling your problems to another person. A GOOD and CLEAN MINDED individual. A Christian, if you want. Not your family, if your family is just.........ugh.
I searched, I found. When I really wanted help. So in reality, no one is coming to save you. Us. We have to seek it for ourselves, on our own.
Aftet this goodness, I sadly reverted back to my old sinner self and this hatred and all this bs has gotten stronger than before. And I've lost the courage to go back and my suicide tendencies has gotten regular and stronger too.
But yea, I get what you mean.. big time
SHARE your thoughts, feelings, any bad thoughts to an open minded and honest person. Real life bonding and connectivity is our best option.. for the both of us.....
Maybe we can do little things that makes us happy.. idk.
Hope this helps, I'm pretty bad at giving advices ssoz