I don't say I'm wimpy in this or that moment to be defeatist or self degrading. I don't say it to comment harshly on being weak. wimpy and weak are not the same. Wimpy is a useful word. I use it to note when I stop, or slow, or want to stop, due to willpower as opposed to physical ability. It's the difference between "I can't keep going" and "I don't want to keep going."
Head game is a huge part of any physical activity, and building willpower is as important in strength training as building muscle. Lots of early attempts at physical fitness are thwarted due to people not getting past the deficit in willpower, which is usually more significant than deficits in physical ability.
It's the reason why couch-to-5k was such a great program for me. It takes you by the hand and has you verrrry gradually build up running time. In my opinion, this is to help you grow how much you think you can run and how much running you can expect yourself to do faster than how much you can actually run.
In my experience, once you build up a baseline of the headspace or of this kind of willpower, you can start really working physically, because this is when you can push yourself to your physical limits instead of your perceived limits.
Since I started hundredpushups.com last week, and since I'd been toying a bit with pushups the week or so before, I have a pretty well developed willpower when it comes to pushups. I really did go as far ad I could today, and it felt good. In a few other exercises I could feel that my lack of ability to make myself do more was hindering me even though my physical ability wasn't. That is wimpiness. And that is one of the things I'm training to work on.
There's nothing wrong with me calling that out, noting where I'm weak mentally or physically to mark the achievement later when I find I'm stronger.