The phrase "didst thing" is an archaic way of describing an action that was taken or something that was done in the past. Today, we might use synonyms such as "performed an action," "carried out a task," "executed a plan," or "accomplished a goal." Other synonyms could include "undertook a task," "handled a responsibility," "completed a mission," or "achieved an objective." Each of these phrases captures the idea of taking action and accomplishing something specific, but in a more modern way that is easier to understand and relate to. Whether you "didst thing" or accomplished a goal, taking action is what matters most.