Self doubt is addictive because it is easy.
Programming our minds to believe that we are too small or too simple is an attempt to relieve the pressure and disappoint that may come with trying to accomplish great things. The problem with this is not that we think we are small — the problem is that we think small things cannot be great. As a result, rather than using all of our small things in the little ways that matter, we let the simple things rot.
When you walk around thinking that you are mold, it's easy to feel like you are incapable; like you are waste. However, in order to have mold you must be porous. This means that you are always capable of taking in new ideas, of learning new concepts, and most importantly, you are capable of becoming part of and even fertilizing a new environment. An environment that exists outside of your self doubt, free of the idea that small means less than great.
In fact, if we were to compile a collection of every small thing that has ever mattered, we would have a list that accounts for everything in life as we know it. The atom, the musical note, the grain of salt, the pen, the idea, the story, the motive, the moments of weakness, the choices — your choice to recognize that your small, simple importance is necessary.
Every single person, place, or thing starts somewhere simple.