I don't have one particular mantra that I use day in and day out, although that consistency is appealing. But something I've been doing more often than not, as I set the tone and prepare to practice is telling/asking myself to let IT go. Whatever IT is that day, and I'm sure you would agree that IT is always changing. This affords me the time and space to notice if I've already formed expectations or apprehensions (guilty), a general opinion of my practice (guilty), and provides an opportunity to move past it.
Now, if you think that your "no victims" mantra is cheesy, then grab some crackers and get ready for this. I am a huge fan of spending a few moments actively, consciously breathing out what I am trying to let go of at that moment. If it's something that I can easily articulate I will even say it out loud (although it's a silent process more often than not.) It's difficult to explain but watching/feeling/letting the IT leave my body, empowers and settles me, readying my mind and body to practice.
Plus, I love to practice in the morning. It's an opportunity to begin the day with intention, discipline, and compassion and my body has always responded well to a morning practice. This breath-based tone-setting of let-go-it-ness, is the perfect way to start not just my practice, but my day.
I know you practice in the afternoons because of Terrible Toddler's schedule, but is that your ideal time of day or a consequence of parenthood?