Act so that you have nothing to be ashamed of in your own heart.
Tips
grammar
无愧 (no shame) + 于 (toward / before). The 于 introduces the standard you're being measured against: 无愧于良心 (无愧于 + conscience), 无愧于祖国 (无愧于 + the motherland), 无愧于这个时代 (worthy of the age). The classic four-character form is 问心无愧 wènxīn-wúkuì.