We receive a prize usually because of our effort and tenacity. To dream of winning the lottery however, places the result of what you experience on others, fate or the outside and unpredictable forces around you.
On one hand, dreaming of winning the lottery shows that you want to win or succeed - or get a lucky break. You can think of winning as giving you the opportunity to experience a sense of 'arrival.' It lifts you above all of your hard effort when you are too focused on the work - and not enough on the reward, or where the work may be leading you. It allows you to re-examine what you value in a way that might change your direction or focus.
Since dreams offer clues about how we can be more fulfilled, and we dream about what we are not facing - the lottery can suggest the need to take action or responsibility to claim your prize (fulfillment). For example, rather than succeed by 'the luck of the draw' explore whether you have a clear vision of what you want - the lottery can indicate how something fulfilling is within your reach - but you may be working so hard you are missing it.
As a symbol of balancing desires against experience - you may be taking responsibility for your success and blaming outside influences when you fail. An inconsistency in your thinking can undermine fulfillment. The idea of a lottery is showing how you are not owning your accomplishments or seeing how failure is not punishment - but often a way of honing your continual success. The message coaches you to connect the outcome - to what you want, or what you are doing. If a specific number(s) was tied to winning - it should be explored as an aspect that is missing in your equation of fulfillment.