Why do I feel so sad and angry and worthless all of a sudden, even though everything in my life is ok?

You may be suffering from a mental illness like anxiety or depression. For a start, i suggest you try to research different mental illnesses and their symptoms. For example, you can watch a few videos of Katie Morton on youtube in which she gives key features of various mental illnesses and what can be done to help solve them. If you recognize yourself in some of those descriptions, I suggest you seek help through therapy and/or by talking about it to people close to you. However, there is a possibility that you feel that way because things in your life are not as ok as they may seem to you. Try taking an objective look at your life. Are there any past traumas that may be haunting you? Is there anything you are anxious about for the future? Is there anything bothering you in your life that you've just been swiping under the rug? I hope you are able to figure it out

There are days where we feel on top of the world and days where we feel sad. Those days are the toughest, where we just don't understand why we're feeling this way, we just are. What we can do is try our best to get back up when we fall. It is okay to feel those emotions of anger and sadness; but just know that you are not alone and there is a support system for you to help you talk through what's going on or just listen when you need someone. Life is hard, but you don't have to go through it alone.

Sometimes it is deeper than you know. I was feeling quite sad for a while until I realized it was from past trauma that I had not dealt with yet. Sometimes taking a closer look at your emotions and what you have gone through helps a lot. Journaling has always been a great way for me to understand my emotions better or even going on a walk, a drive or simply listening to music. Also allowing yourself to feel your emotions instead of suppressing them can make a world of difference (it did for me). Don't be afraid to let out your emotions and feel what you are feeling.