In life, sometimes we set goals to achieve things--it could be a career goal, relationship goal, personal goal, etc. And then we you get there, you achieve whatever it is you wanted and you realize it just doesn't matter to you anymore. And the more that happens, you see the futility to tying yourself to the future. Of thinking that something out there is going to make a difference in the quality of your life. Because life as John Lennon so aptly stated, "Life is what happens while you're busy making other plans."
There is only now. Our thoughts about the past or the future only happen in the now. There is no other moment but the one breathing its way through you right now. And there's a certain magic to the present and your awareness of it. You can watch all your thoughts roil by like clouds on a sunny day. They're just there. There's no attachment to them. You don't feel the need to define yourself by them. They just are.
Of course, being in the moment does not preclude planning for the future or looking at the past. The difference is in noticing that you are here in this moment and in this moment there is choice. We get to reinvent ourselves each day. We can choose and choose and choose again.