Never regret a day in your life.
Good days give you happiness and bad days give you experience.
Both are essential in life.
All are God's blessings.
We have all wasted time regretting things from our pasts. Regret is something that affects every single one of us, but in actuality it affects us all differently. Some of us are able to think about mistakes of the past, and take the lessons we learned from them into our futures to help provide ourselves with a much better life.
While some of us are never really able to get over the steep pain of the past, and never are really able to focus our energy on our futures until we learn we have to change our focus. If you can shift focus from rearview to front view, in a matter of time, you will change the direction of your life.