The less you attach your happiness to people or material things, the happier you'll be.
Because material things come and go, as do people. They're transitory.
What brings us true joy are experiences, which can create lasting memories.
While things may have ended badly with your ex-boyfriend, there's no harm in conceding that you cherished -- perhaps to this day -- the times you spent with him, even if you don't want him back in your life.
Or, you may reminisce about the trip you and your friends took to Cancun while you were in college, even though time and distance have caused something of a rift in your friendship.
See what I mean? Focus on the experience and how it enriched your life, not on the person. Relationships evolve just like the people in them. Depending on someone else to be happy sets one up for disappointment in the event that person does a one-eighty, which most of us have experienced at some point.
You can love and appreciate someone in your life without relying on them to be happy.
The same goes for material items like shoes, cars, and gold watches. There's no harm in acknowledging that it feels great to wear them, that they make you look good.
It's when you get in the habit of going on shopping binges when you're angry or depressed that one thing becomes evident: you depend on material stuff to make you happy and improve your mood, and that's never a viable strategy in the long run.
The most "material" thing I depend on to give me a boost? That would be books, hands down, but it's only because of the rich experiences I derive from them.
They allow me to escape reality and learn new things. They're nourishing for the mind. The knowledge I gain from reading a book will stay with me forever (until I lose it through memory loss and old age).
While people and things can add value to your life, you should never condition your happiness on owning a certain item, having a certain job, or gaining someone's acceptance. Doing so will only lead to a host of negative feelings, like bitterness, anger, sadness, and envy.
Instead, rely on your experiences for personal fulfillment. You can cherish them your whole life and, once committed to memory, they don't change -- unlike people and objects.