There's always a fine timeline of the perception of your moments.

When everything goes well you keep flying high.

When everything deteriorates you keep sinking down.

Whether flying high or sinking down the timeline is yours only and it's constant.

As you move ahead and look back at your timeline you are able to see things differently.

If your then moments associate to a till this day flying high set of memories,

only the positive sub-memories associate, and all the rest is neglected.

Else if your then moments associate to a till this day sinking set of memories

only the negative sub-memories associate, and all the rest is neglected.

However only if your then moments associate now with no feelings at all,

only then your mind can be crystal clear in order to give you the proper perception-free judgment.