Do you talk to yourself while you're working out? Serious question! Or would you rather not be the person everyone avoids on the gym floor as they're worried about the mental state of someone happily having a conversation with themself?
Do you respond better to motivation? Could you push out a few more reps or go just a little bit faster with someone there to encourage you? I'm guessing most people would say yes - which is perfect as it keeps us Personal Trainers in a job! So if you respond to someone pushing you to the next level, getting the very best out of you, motivating you to try those last few movements - why can't you be your own cheerleader?