Have a good look at what you've got, there must be a reason you bought such and such an item. Enjoy it, you paid for "it". So many times we buy things out of obsession for silly reasons like my best friend has one. "The grass is always greener ..."
To ask this you're obviously not satisfied with what you've got, and I suspect it's to do with a relationship, or money (Work/Career) . Make a plan to write a list of what you like, what you have that you like, what haven't got that you would like to get. Once you define these things try to put forward a course of action to gain happiness by achieving the things you really want in life.
We always want what we can't have - it's human nature. Not the easiest thing to deal with, but you have to try and adjust your mindset. You have to try and convince yourself that you don't need anything more than what you already have.
because its just human nature to want new things, not just to buy new things either. we like new sights, sounds, tastes, etc. try doing new things and get out of boring routines, then maybe you'll be happy with what you've got.
because it human nature t always want better, and want more