Be positive and the challenge will be easier.
Self-defence, self-confidence, discipline and self control. The values you learn are priceless.
A strong body is a good asset. A strong mind is a very good asset.
If you are not comortable to deal with an opponent 50 lbs heavier than you, there is something wrong with your Jiu Jitsu.
If you believe, then you have already taken the first step towards your achievement.
If you do not speak up when it matters, when would it matter that you speak? The opposite of courage is conformity. Even a dead fish can go with the flow.