heart......

Oxford Dictionary
heart:

1 a hollow muscular organ maintaining circulation by rhythmic contraction and dilation.....

2 regarded as the centre of emotion and feeling

1 makes me think of words like:
            attack, failure, beat, transplant........

2 put heart before or after:
           good, gold, to heart, ache, broken, courage, after my own...

both have to do with life......each in a different sphere....
and equally important.....

hearts are fragile....and break easy.....