I went for a half hour row in the gym tonight.  I just wanted to row for the whole 30 minutes, because I found it hard to sit for that long rowing last time and it would be an easy move back into training.  I wasn't worried about making a distance target.  As it happened, I got over 7,400 metres, which is still ok for this row.

I prepare for the row mentally by breaking it down into 15 x 2 minute pieces.  It doesn't take much to row for two minutes and I only need to countdown 15 of these, so it feels manageable.  Similar to long distance running, part of the method is mental.