At least to myself, to admit I am "strong" would mean I'm putting some sort of cap on something that has a limit. It'd be kind of like working on a project for years only to wrap it up with a pathetic "yeah that's good enough". I'd be doing myself a huge disservice in this way because at that point my goals would become measured to receive some sort of ending that doesn't exist.
Just like you can't shut your brain off because you've learned everything there is in the world (or at least you shouldn't), you can't let yourself get convinced you've hit the pinnacle of strength ever.
There's always room for more and that's why I am a STRONG believer in HUMILITY. Humility is what separates the successful competitors from the mediocre. Humility means you know two things as a successful athlete. One you know that if you think you've hit a limit there is always more and two that there's almost always someone out there stronger than you so there's still room to improve.
Vice versa you have the lifter who's a big fish in a small pond. In the comfort of their own little gym they think they're the best because no one else can match them but being the "best" is also the nail in their coffin and the biggest detriment to their strength.
The solution? Opening your mind to seeing what's out there. Actively seek out new opportunities to put yourself outside of your comfort zone. This may mean joining a new gym where you're the smallest person, pairing up with a new training partner who reps out your max, or even just going out to the next local/national meet to watch the lifters.
Some people can be intimidated by this but that's is why I choose to train with people stronger than me. It's a fresh reminder that there's room for me to improve but also a strong motivator showing me that anything is possible if you push your limits. As long as their is someone there to load up the bar and demolish big numbers; I know I'll always make progress.