As Whitewarrior implied, sensing another person's energy is VITAL to safe healing. If you have difficulty sensing energy then that should be the first thing you work on. Manipulating energies is always easier than sensing them. Chances are, if you are attempting to make an energy ball then you are succeeding... but you are simply not aware that you are succeeding. Next time, instead of concentrating on the creation part, assume that you were successful and just feel for the edges of the ball.