Definition of think back in English English dictionary
If you think back, you make an effort to remember things that happened to you in the past. I thought back to the time in 1975 when my son was desperately ill Thinking back, I don't know how I had the courage. = look back
recapture the past; indulge in memories; "he remembered how he used to pick flowers"
In imperative form, advice supposedly formerly given to women before sexual intercourse with their husbands. (often associated with the Victorians, though not attested until later). "think of England" refers to the importance of children