Some of the strongest people I know are the ones who have been through the most in their lives.
The idea being, of course, that strength is found in proportion to the number of adversity/challenges/obstacles faced and moved forward through.
Which means, if you want to be a strong person, it would be in your best interest to develop your courage so as to better face the adversity/challenges/obstacles of your life and then to invest in your spirit which is essentially the horse that pulls the carriage (you) forward and through whichever of the above mentioned experiences you’re facing.
If you want to develop your courage, remember that it feels the same as fear—you’re just choosing to make a different decision in spite of that feeling.
And if you want to develop your spirit, remember it feels similar to faith—you’re not sure exactly how it will all turn out, just that forward and through will lead to a better turn out than running from and away.
Without courage, you’ll never even face the correct direction (towards strength). And without spirit, you’ll be an abandoned carriage without its horse—moving exactly nowhere.
If you want to be strong, remember this and invest in courage and spirit.