Every kind of satisfaction you get out of external phenomena is temporary, fleeting. Whenever a drug, or a game, or a pleasant conversation, or having sex, makes you feel satisfied, you are quickly unsatisfied. You need another fix to get that feeling again, but it often becomes less and less satisfying the more you do it.

Think about it- can you play the same level in the same game over and over again and still have it be as enjoyable as the first time you did it?

Can you spend all of your time, 24/7, for years and years with a significant other and still find her as pleasant as when you were initially attracted to her?

No.

So, clearly, happiness is not inherent in these things, because if it were they would always, objectively result in happiness when you associated with them.

And whether it is even enjoyable at all is dependent on how you relate to it.

So, it is then that happiness is something that comes from your mind and is not reliant on things outside of you. (not to say all external phenomena play absolutely no role in any aspect of happiness, however).

Therefore, relying on things like relationships and toys to provide happiness is inevitably going to lead to dissatisfaction.

In order to find happiness you have to cultivate it within yourself. The way you view phenomena in general, the qualities and habits of your mind.