Good question, but do you determine your strength by the challenges you conquer? If so, then having challenges to over come will bring you a sense of that 'strong man'. Either way, over coming challenges will always bring that sense of accomplishment, but I would dare say that it is not the determining factor for your strength.
I'm assuming we are talking strength of the mind and heart? If so, then your strength is determined by the ability to make conscious decisions without allowing your emotions to do the deciding for you. The ability to be ready to over come said challenges, and do whats right, even if the most influential person in your life tries to convince you otherwise.
And most importantly, the ability to change yourself for the better. No one is perfect, but we should always strive to be a better man, woman, spouse, parent, sibling, etc. The only thing in your way of that is obviously you, but to jump the hurdle that is yourself and to let go those fears will truly determine those strengths.
On a personal note, my wife and I did the Love Dare. I recommend it for anyone wanting to be a better spouse, but it touches on so much more than that. Its basically a 40day step on how to show a love that stems from your consciousness and not one that is effected by your day to day emotions.
Good luck, God bless, and I hope this helps!