One can not know nor appreciate fully the depth and breadth of a kindred, eternal loyalty, acts of kindness and generosity, or love's universal brilliance and reverent spirit having not at some point in life walked the void, desolate and parched landscape of absence.
We all know people who have walked the walk, and not unlike the snowman rolled into existence from the driveway who is given lumps of coal with which to see for the first time, the view is priceless.
Living in or worrying about the past, or about something once done that you could have done better is a useless endeavor - for no amount of energy can change the past. The future is still to unfold and may never be, and so waiting today in anticipation of something tomorrow is just as fruitless as is your lamenting the past. Our only time to truly live is in the present - this moment - and to do all that is doable.