The trick is to pick a partner that plays pretty much the same patterns that you do. Then let them know up front that anything you do to screw up is not done intentionally, (No, I did not mean to scratch or leave you straight in or on a rail!) and that you know he won't either.
Then play your own game. Don't worry about leaving them perfect or you will screw up. Have faith that your partner can make the ball from anywhere or think smart and play safe, and vice versa. Play as you would play for yourself and that is the best advice I can give you.
I have won tons of scotch tournaments (once I won 3 different tournaments on 3 consecutive weekends with 3 different partners) and I can tell you, I have had the most success with low-key players that don't get upset. (Read, not my husband!)
Glenn Atwell and I just finished 2nd in Scotch at the BCAPL Nationals in Vegas. And he is about as low-key as you can get. Even when they forfeited him matches in 10 ball because we were playing in the Finals.
It is counterproductive to your team to get mad. Everyone makes mistakes. Just carry on and forget about it. Your partner feels bad enough already.
One tip I have is to let the best player follow the breaker. Since I am assuming you both have good breaks, it is best to let the better player follow the breaker because he will determine choice of group and get you started with the right shape to run out.
It is true that the weakest link determines how strong the team is. And also that we call it Scotch Troubles or Divorce Pool. I can tell you stories that would make your hair stand on end! ROFL. But it is a fun game that you will enjoy if you just go with it and don't stress out too much. Good luck!