This moment is here and will be gone. The next one will come and go. As you think about it notice that each moment comes and goes and is no longer here. They become the past. The ones that come to you are in the future not yet here. Imagine a string in front of you like a necklace with beads attached to it. As you pass the beads through your hands each one is here for a moment and then gone. You can hold onto the bead for as long as you want or pass it by quickly and move on. What happens in the time that you hold that bead in your hand is that you focus on what you are doing right now in this moment.
Now take this analogy up a notch (no pun intended). Instead of holding a necklace of beads on a string you are holding a line of time, your time. This time is continuous and never ending. You can not see back to the beginning nor far in the future. You can though know what just occurred, the memories of times gone past. Likewise you can anticipate future events and plans. Noticing these individually on their own you will see that they are just what they are moments, right? Nothing more than that.