Making yourself stronger and opponents weaker: It's a great thing to be physically strong and it will definitely help you in any match. As such every Jiu jitsu athlete has a responsibility to work diligently on their strength and other physical attributes. Nonetheless, the ideal of Jiu jitsu is always to put the primary focus on MAKING THE OTHER FELLOW WEAKER RATHER THAN YOURSELF STRONGER. The human body is set up in such a way that it can exhibit impressive strength in good postures, but is pathetically weak when those postures are broken. For example, you can make the strongest arm feel very weak indeed by putting it behind the strongman's back. If you can maintain good posture while breaking that of your opponent you can create the impression of greater strength even when grappling opponents who are objectively stronger than you. You know you're doing well when strong opponents are praising you for your strength when you know damn well they are stronger than you.
