This one came from the Derek Sivers and the idea is short and sweet.
A marathon is not difficult, it is hard. You put on shoes and run 26.2 miles. It's quite simple actually, no crazy instruction or steps to follow...just run! BUT, a marathon is extremely hard. It is grueling, painful and challenging...hard!
It's important to differentiate between these 4 words to better help you deal with and plan for challenges in your work and business. Getting your finances in order might be simple but hard. Simply set a budget, do your best to stay within budget and follow the rules you set. But getting your finances in order might be mentally hard; making sacrifices, saying no to certain things in order to stay disciplined is hard work for some folks.
At work a project might be difficult but easy. If larger complex tasks are broken down to smaller subtasks and communicated, delegated and monitored effectively you can conquer the difficulty of the task and deadline. This work in turn might be easy!