Final answer:
The phrase 'difficult or impossible to believe' suggests something is unattainable. In the context of goal setting, it is vital to ensure that goals are not only achievable and realistic but also relevant and time-bound.
Step-by-step explanation:
The definition of "difficult or impossible to believe" can be related to goals that are set to high and, thus, may seem unattainable. When setting goals, it is essential to ensure they are achievable, which means they should be realistic, within reach, and any barriers should be surmountable. The goals should also be relevant, meaning they support other objectives or long-term aims, fitting within an overall plan or purpose. Furthermore, to be attainable, goals need to be time-bound, having a specific deadline or target date that encourages prompt action and provides a clear timeframe for completion.