Write your epigraph with your life while you can （strive for a brilliant one）.
Engrave your own epigraph with your life while you are able to （ make great things happen）.
Use your life as a graver to write the best epigraph while you can （make a great one）.
第一和第三句中的“one”都是指代epigraph
没有逐字翻译,基本上是英文怎么顺畅怎么写的
另：括号里的可要可不要