How to stay motivated when you are a lone employee in a start up

Before businesses go big, before businesses become MNCs and before businesses start dolling out money, there was just one person. A lone entrepreneur trying to get an idea working and get a business rolling. When Apple first started in a garage, at least Steve Jobs and Steve Wozniak could support each other. You, on the other hand, have to bare the burden on your own. Creating a successful business is just like climbing up a mountain. It is a step by step process which is very difficult and at every moment, part of you wants to call it quits and at times, you may have almost reached the peak. So how do you keep yourself motivated and continuously push yourself to not give up on your dream?