Hi,
To me, it would be more natural to omit the "so", or to replace it with "often." Since you begin with a conjunction, it should be all one sentence, with a comma after "ruthless." If you want to use two sentences for emphasis, just skip the conjunction. "The truth is so harsh! You have to accept it anyway." (That's my opinion.) You could also say, "The truth is harsh, but you have to accept it anyway." OR "Although the truth is very harsh/ruthless, you have to accept it anyway. "So" doesn't seem to work except as an exclamation, or in answer to the question, "How harsh was it?" - "It was so harsh that - - - - -", ala Johnny Carson and Ed McMahon.
- A.