Romanized:
Enryo nashi de, genjitsu-teki ni ikiru.
Literally:
Without modesty (i.e. worrying what others may think about you), realistically live.
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Here's a shorter version, which might be better for a tattoo:
現実的。
遠慮なし。
Romanized:
Genjitsu-teki.
Enryo nashi.
Literally:
Realistic.
Not Modest.