I think freedom falls under possibility, and that possibility is the real answer to this question. If you are capable to do the things you want. For example, if you want to travel, it's possible for you if you have the funds to do so, you have the infrastructure to do so (e.g. airports, means to get to the airport), you live in a country where you are able to travel freely (this is where freedom comes in). As you reach higher places in your life, you have a higher ability to do whatever it is you like, and are generally more happy. Someone who has a minimum wage job at a record store without the ability to take vacation time is not going to be happy if they want to travel, but their coworker who desires to drive down the coast on the weekends and make suggestions on music to customers very well may be in the situation most conducive to his happiness.

of course, most people's aspirations and desires require more resources to achieve, and that's why money generally does improve happiness to a certain degree, but stops doing so once they've achieved the necessary level for themselves.