From personal experience, I believe that negativity and especially self-negativity are very bad. They stop you from reaching the places that you want to get to in life.
You clearly have tried to be more positive. But unfortunately, since it has not improved matters for you, you feel you have failed. And because you have failed you have become even more fearful, anxious and negative. This is a common cycle and many people have experienced this.
Typical examples of negativity, and especially self negativity, include:

Am I good enough? No, I am not clever. I don’t think I am fit for this.
I don’t want to participate. All are doing so good. They are much better than me.
Others have better friends/family/wealth than I do. What am I doing wrong?

Whilst awareness is the first step, what is usually missing in here is, the fundamental desire and intent in wanting to change your mind-set. Remember that your biggest critic is yourself.

Remember, Thomas Edison, the renowned scientist, while talking about his failures, said, ‘I have not failed. I have just found 10,000 ways that won’t work’ after attempting to create the lightbulb 1000 times.’

•Thus, remaining positive is about recognising that even failures are a positive – and the key to becoming positive is your very own self! No one can make you miserable or negative: only you can! It is because you choose how to respond and interpret what people do or what happens to you!

So remember if you want to be positive and happy it is entirely down to you internally.
How do I overcome this self doubt and negativity?
There are numerous positive thinking strategies but fundamentally you must have the pure inner intent to genuinely want to not listen to your inner negative thoughts but instead want to move to a positive mind-set.

•The best way to change this mind-set lies in realising that your existence is to serve others and appreciate the world around you.

•Do not allow yourself to be surrounded by other negative people but instead ensure you are in a positive supportive environment with people that are highly energetic and happy!

Param Pujya Dada Bhagwan suggests: ‘If you want to take out air from a bottle, you fill it with water and the air will automatically come out. In the same way, when you pour positivity within you, negativity simultaneously evaporates.’

•A good method to fill this kind of positivity is to chant any mantra eg. ‘Dada Bhagwan na aseem jai jaikar ho!’ by closing your eyes and visualizing every letter of the mantra that you utter. This helped me ease out the negativity and fears residing within me and I began to cope well with both my social life and the other parts of my life too.

•Finally, in the Akram Science, as propounded by the spiritual leader called Param Pujya Dada Bhagwan, it is suggested that we are a Pure Soul, and hence we are full of infinite strength; so we should indeed think of this when facing failure and unhappiness, and look forward to attaining Self-Realization in this life itself so that we very well realize that really who am I.
(For details, you may visit:- https://www.dadabhagwan.org/self-realization/. You can also get more solutions regarding fear and anxiety at https://www.dadabhagwan.org/search/fear/)

Author's Bio: 

Ambalal M. Patel was a civil contractor by profession. In June 1958, spontaneous Self-Realization occurred within Ambalal M. Patel. From this point on, Ambalal became a Gnani Purush, and the Lord that manifest within him became known as Dada Bhagwan. A Gnani Purush is One who has realized the Self and is able help others do the same. Param Pujya Dada Bhagwan used to go from town to town and country-to-country to give satsang (spiritual discourse) and impart the knowledge of the Self, as well as knowledge of harmonious worldly interactions to everyone who came to meet him. This spiritual science, known as Akram Vignan, is the step-less path to Self-realization