Modest, reasonable or unreasonable aspirations – what’s best? coach asks

A speaker at an evening I was at recently said "it's ok to have unreasonable aspirations". She said this to explain her story of having a vision for a new business and despite all odds, over a period of years, created exactly what she wanted. She spoke of the people who said her ideas were unrealistic and unachievable; and spoke of the small core of people who believed in what she was creating. I have since reflected many times on her comment – it's ok to have unreasonable aspirations – and wondered how many of us stick with modest, reasonable aspirations because they're safer, when deep down we may want to aim much, much higher. What about you? How modest, reasonable or unreasonable are your aspirations? What may stop you going from reasonable to unreasonable?