You can't drive a car by always looking at the side mirror.
More or less 99% of the time you're driving, you have to focus on what's ahead.
Every now and then, especially when you're changing lanes, you have to take a glance at your side mirror. You have to take a few glances on what's behind you.
But, most of the time, you have to keep your eyes on the road.
Similarly, to go to where you want to go—perhaps a dream—you have to focus on what's ahead and not on what's behind.
You can take glances though, especially when you're changing lanes or changing direction.
You can take recall the lessons you learned in the past. Or take a short look back on the good things that happened in your life. Then, shift your focus on the road ahead.
When your past didn't go the way you wanted it to, all the more that you shouldn't focus on it. Just take a few quick glances and then shift your focus.
Where are you looking at more often? The road ahead or your life's side mirror?