this one needs some practice. Don’t get yourself discouraged, don’t give up. When you get frustrated, rest and stop for a while.
Basically string placement is REAL critical in Double or Nothing. Try to get the string on your throw hand as far inside to your index finger as possible. Remember, practice makes perfect. PRACTICE PRACTICE PRACTICE. Also don’t blindly practice too. Look through your mistakes and bear them in mind. try again with more cautious. Once you get it, hallelujah ! You can advance to more complicated string tricks then