In this way, your every meal can be delicious, almost every experience a positive one. This is actually a major secret of being happy with one's lot in life. If we don't look at what others have, and based on this form expectations, then we can very easily enjoy whatever it is that we receive.
The Mei Shiloah explains that this was Yaakov Avinu's midah, that he had no desires for anything other than what was his, he didn't feel a lack of anything. This was the meaning behind איש תם יושב אוהלים - a simple tent-dweller.
Rebbe Nachman takes this idea in a slightly different direction and explains that just as HaShem creates us new every day, we need to interact with HaShem and the world with this knowledge. Every day we should serve HaShem anew, with whatever is given to us in this day. This is the extreme version of the idea of being unexpecting. Not only don't we have expectations about our life, but every day is itself a new surprise.
Rebbe Nachman basically explains that this is the secret to staying young at any age, and judging from the elderly people that I've met, the happiest seem to have arrived at a similar understanding to that of Rebbe Nachman.