When you treat things or circumstance you have in your life as though you own them, eventually, you will take those things for granted. Having the mentality of owning things results in attachment, responsibility, and worry to those things you think you own.
Ask yourself what do I think I own? and see how much effort, worry, and responsibility it takes owning that. It could be your house, car, relationship, job, money.
If you ditch the mentality of owning and substitute it with the mentality of having, you will appreciate in a non-detachable way everything that you have in your life and free yourself from ever worrying about losing something or missing out. You will see that everything that you need right now is already in front of you, without you having to do anything or worry about keeping what you have.
If you drop all your worries about the future and all attempts to figure things up right now you will see that everything is just passing you by. Clinging or attaching yourself to something, in particular, will make you suffer once that thing will pass. Instead, choose to express unattached gratitude towards having what you have, experiencing what you have. Know that you will always have an experience filled with everything that you need in every moment.