Look back to understand how yesterday affects today.
Determine which past choices should continue into today.
Determine which new choices will avoid the repeat of past disappointments, moving you positively towards the future.
Sing and live in the present, with an eye to the future.
Progress (technical, artistic, and otherwise) will be guided by self-knowledge of past performance, but you have already dealt with the past. Continuing to look back only distracts and discourages you, wasting energy and time. The eye to the (not too distant) future helps you to make current choices that yield future options. This translates into constant transition–a concept I often use in the studio for resonance, musical line/momentum, etc.
Do give yourself the option of occasionally looking back at successes (we will define “success” later), to be reminded that you can expect similar–even greater–successes in the present and future. After all, those successes were not random, once-in-a-lifetime happenings… Keep moving ahead!