Why do I feel so inferior and worthless and useless all the time?

You may be focusing on all of the negatives instead of the positives things you have done. There will always be some form of progress no matter what as long as you apply yourself.

You got to change howb you think. Stay positive and have positive reminders around. Cause you are none of those things

Mostly because you don't self-appreciate while overly-appreciating the laurels of others and sometimes, even exaggerating them. Look towards the positives in you and start rewarding yourself for them.

Because of your past experiences. Due to others behavior towards you. There could be many reasons which could make you feel inferior. To feel better, remind yourself about the good things you did, the efforts you made to achieve something, your milestones, accomplishments, good memories and positive thoughts about yourself. It will help you to feel better.

You put too much pressure on yourself, you compare yourself to others, and so than measure your worth and effort based on how you add up. When It all comes down to your own pace, and how you see or define yourself overcoming this obstacle soon or in the long run. Doing things doesn't have to seem like it's a destination rather, seeing it as a journey and enjoying the journey rather than the destination can put things into a better perspective in how you see yourself and experience the project, sport, activity, work. At least doing things with a clear conscience and at a pace, you can manage brings more clarity, understanding and experience.

some people may feel that way because perhaps they've failed at something once & instead of trying again, they just stopped and let the failure take control.

Because you've convinced yourself you are that. As the saying goes: Before you consider yourself an idiot, make sure these around you are not themselves idiots.

When we compare ourselves to others we loose track of how amazing we are as individuals there something that we can do that other people can't and things other people can do that we can't. We are all individuals and no one of us are alike we should try to be the best that we can be and not compare ourselves to others because we're not them.

My guess is either stress, depression or anxiety. So many people have one or the other or maybe even more than one. It's okay.

You may feel worthless and useless because you feel as though you don't make a difference. But you by all means make a very being difference to the world. I know as a fact that I'm worthless and useless but that doesn't stop me from trying my best to be useful. I don't have the ability to do so many things, mainly because no one tought me or I was too scared to try. So right now I'm trying to listen to as many people as possible and help them with their troubles. Helping people like this is the most that I can do to be useful at the moment