If I divide the sentence into parts,
It's just that, the question/problem of whether it cannot be fixed or I cannot fix it, has turned my sadness into frustration
This problem has made my pride/obstinacy/stubbornness and my kindness/friendliness turn into this weird combination where there is an overlap between the will to do it all over again i.e., fix this and my strong obstinacy/stubbornness.
I am a good for nothing human.
I don't know if my translation for the second part is correct but the way the second part connects with the third is something that I have trouble understanding. Why does 強さが abruptly end with ダメ人間. I thought the second part was an attributive clause but the が ending makes me think otherwise.
Thank you :)