Have an aim without an ambition.
There is a crucial difference between having an aim and having an ambition. Ambition suggests incompleteness, as though your life will not be okay until you reach a distant conclusion. When you are ambitious, you treat your entire life as though it were a long line to get into the Empire State Building: You may not enjoy where you are right now, but you think it will pay off when you make it to the top. But it never does. Ambition will ruin you. It will cause you to treat everything and everybody you encounter as though they do not matter when compared to a greater thing you haven’t even experienced, and possibly never will. Ambition causes you to lose sleep, lose friends, and (ironically) lose motivation to achieve the very outcome you are so anxious about.
Ambition is an impotent “must.” There is no worse feeling. An aim, on the other hand, merely means that you are moving in a certain direction, but not trying to rush through anything (or anybody) along the way. An aim is what you have when you take a fun walk through Mahhattan. Yes, you may be on your way to the Empire State Building, but you are in no terrible hurry to get there, and you have planned many stops along the way. You figure you will arrive eventually, but you feel no sense of urgency about it. You walk through the parks. You let people cut in front of you, not because you're a pushover, but because you don't care. It’s a nice, breezy walk through the greatest city on Earth.
Also, if your friend calls you while you're at the coffee shop and invites you to eat steak (his treat!), you have no reason not to go. After all, having fun in unpredictable ways was the entire point of taking this walk in the first place. Your decision to "see the Empire State Building" was simply a decision to walk in the direction of the Empire State Building. You would be a fool to rush past serendipity. Even supposing you were to reach your destination quickly, then what? You would then have to make up a whole new destination just to keep yourself from being bored for the rest of the day. You’re better off enjoying every moment of your journey. Even if you die before reaching the end, so what? The good life is available immediately; you don’t have to wait. In fact, the good life never comes to those who wait for it. It only comes to those who have resolved to make the best of where they are right now. To summarize, your perennial goal must be to live well today — not later. In order to do this, you need an aim, simply because an aim gives meaning to each day. However, you must avoid the disease of ambition, because ambition collapses your entire life down to nothing more than a means to an end.
I did, in fact, take a walk in Manhattan yesterday. It was nice.