"Let your eyes look straight ahead; fix your gaze directly before you" (Proverbs 4:25).
One of the main rules in competitive running, or racing of any kind, is that you don't focus on who is behind you, but on what is in front of you. Concentrating on behind only slows you down and increases the risk of "crash & burn."
One reason it's so hard for many to achieve what they've set out to achieve is that they don't look straight ahead at their goal. Or, perhaps they're not sure what there goal is, thus just traveling aimlessly, hoping to get somewhere, and hoping that somewhere is some place good! But, you'll never hit that target straight ahead if you're focused on your surroundings or on your past. You must be intently focused and purposed on the goal ahead.
This is where I, and I'm sure many, can easily struggle. We begin by seeing the big picture, but then allow ourselves to get distracted by "other" things. I'm sure you can fill in the blank for you own "other." We start things and don't follow through with them. We must be intently (focused) looking ahead, not being distracted by all the things going on. We can be, and should be aware of what's going on around us, without them becoming our immediate focus.
You can't be focused your past, whether it's mistakes, successes, or the like, but focused straight ahead to what God has called you to!