You just have to remember this... Life is cyclical, as is nature. Things always return to a state of normalcy, although this state may change from time to time, or situation to situation. But nature always balances out.
Life is like that. A lot like that. We all have a place in the cycle. This cycle will present us with good times and bad, and times where things seem entirely neutral. But nothing ever remains the same. You may be in a low period in the cycle now, but at some point things will start to get better... How long that change takes is dependent upon a great deal of things, some of which are beyond your control. But you do need to be able to see that "silver lining" in things.
Life is a wondrous thing, which we are given precious little of. IMO, we are placed here to find our path through a treacherous current, and we have been granted the spirit to change our outlook, our mood, and our environment. We must seek the maximum enjoyment possible from ourselves, each other, and the world around us, but maintain a level of self respect and determination to avoid those things that would disgrace ourselves in our minds' eye.
The question you've asked can only truly be answered by ourselves, and the answer can only be found in ourselves. I would encourage you to try and change your outlook, and find the root of this question that is gnawing at you, to analyze and understand why it causes you such grief. Then, and only then, can you begin to change your perception's. And then the cycle will begin an upswing.
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I myself started having such nagging doubts in the middle of my sophomore year. My grades began to suffer, I began to withdraw from all but a few of my closest friends, and I began to think of suicide. I never attempted it.
I spent a lot of time alone, questioning myself, my worth, and my future. I had, and still have, alot of fears about my future. We live in a strange and uprooting time, no doubt about it. I saw how bad things were becoming for everyone, how the job market worldwide was suffering, and saw how people were losing their jobs, their homes, their lives... I didn't talk to anyone about my secret fears. I just kept asking myself the same question over and over... "Why am I set upon with such doubt?" It took me until the middle of my junior year of high school to figure out why.
I was afraid that any attempts at education after high school would not only be prohibitively expensive, but that the job market would have shrunk by such a degree as to effectively make it impossible for me to be hired for any entry level position, without a ridiculous amount of education... I couldn't stand the thought that I would be possibly saddled with $100k + in debt, without a means to begin paying it off. That my average-ness would make it nearly impossible for me to get into a good college in the first place, and that I would disappoint not only myself, but my parents.
I had a hard time finding reasons to get out of bed in the morning. I would wake up, and spend 15 or 20 minutes trying to talk myself into going to school. I didn't pay attention in my classes, wished the day would end, was thankful for snow days, or two hour delays, where schedules would be disrupted, and we wouldn't have to do any work. I stopped doing homework altogether, not seeing the point in it. Eventually, I was able to meander through this period, and am feeling all the better for it.
I decided to change one thing that I didn't like about myself at a time. I started with my weight. I started to do some push ups, sit-ups, and stretches before bed. I started snacking less often, and eating smaller servings at meals. I lost 15 pounds, gained some decent muscle mass, and lost some of my flubb...
Then I decided to change my hair style. Weird, I know, as a guy, but it helped. I had had the same basic hair style for the first 15 years of my life. It used to comb it to my right, and left, from my part line. I decided to grow it a little longer, and slick it straight back. It helped.
Then I decided to start doing my homework. Started paying attention in my more important classes, and my grades began to improve. My math teacher expressed her relief that I had started doing better. I began to feel better about myself.
I decided that I needed to keep track of my future better. I decided to keep an eye on a few key stocks, from various industries, to see how the market was actually doing. Eventually things started doing better.
I began to read more books on wildly different aspects of history, from the ammonium-nitrate producing system invented by Carl Bosch, and a 1st World War German scientist, to autobiography's of our founding fathers, to books on how society changes throughout history. I started to understand that life, and nature, is cyclical, and all good things exist because of the bad, and vice-versa.
I don't have to talk myself out of bed in the mornings anymore. I go to school, while not exactly positive feeling, with at least an interest in a few of my classes. I've begun to make some more friends in different groups, and re-connect with old ones from my old stomping grounds.
I feel better now than I have in 18months, and I know that when I wake up tomorrow, I can expect at least one thing to be a little better than it was yesterday.
I still haven't talked to anyone about this yet, and, truthfully, I don't know if I ever will. But I've begun to understand that life is going to hi you hard, but you always have to get back on your feet, or it will just keep pounding on you even worse.
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I hope this has helped. If you need anyone to talk to, please feel free to PM me, any time.