उद्यमेनैव Only through effort (resolve) are tasks accomplished सिध्यन्ति Succeed, achieve completion कार्याणि Works, tasks, or actions न Not मनोरथैः By mere wishes or desires ।
न Not हि Indeed सुप्तस्य Of the sleeping सिंहस्य Lion (symbolizing strength / potential) प्रविशन्ति Enter, approach मुखे Mouth, the entrance मृगाः Deer (symbolizing the objective) ।।

"Only through effort (resolve) are tasks accomplished, not by mere wishes.
The deer (by itself) do not enter the mouth of a sleeping lion."