Relegation candidates early in the League Two season, Shirtliff replaced Carlton Palmer as manager in September and has since hauled the Stags into 12th place.
But Shirtliff conceded any hopes of a play-off finish were dashed by Saturday's a 2-0 reverse at the Memorial Stadium.
And the Stags boss was also left to reflect on a disappointing nine points taken from a possible 27 over Christmas and January.
Shirtliff said: "We were a little unlucky not to pick up many points through the Christmas and January period.
"But since then we've kicked on and done well although we still have to eliminate the errors and be tighter."
But Shirtliff conceded any hopes of a play-off finish were dashed by Saturday's a 2-0 reverse at the Memorial Stadium.
And the Stags boss was also left to reflect on a disappointing nine points taken from a possible 27 over Christmas and January.
Shirtliff said: "We were a little unlucky not to pick up many points through the Christmas and January period.
"But since then we've kicked on and done well although we still have to eliminate the errors and be tighter."