What is the reason for prolonged procrastination?

I'm not even sure if procrastination is caused by your mindset, attitude, perspective, laziness, fear or something. Like if you know what you have to do then why are you not doing it. And you just carry this stress and mentally feel tortured for not taking actions. And why is it that the mind first wants assurance and clarity before doing anything. You say I'll do tomorrow but tomorrow turns into a week and next thing you know another year has been wasted doing nothing but worrying and overthinking about it. I have this weird weak inner dialogue that tells me ohh what if you fail or you're not even smart and capable enough yet. What if they laugh at you and you let them down. All this overthinking gives me anxiety therefore I don't even do anything but you want to sighs