I for one find it very hard to pen down my own experiences, specially the negative ones, for these very reasons.
It's easy to talk at lengths of our happier moments and more positive traits, but to analyze our downfalls and life's trialing periods can be soul searching and very strenuous.
I've always found it easier to express another's, be them for real or fictitious characters, emotions in words than my own. Back in my teenage years I used to write all these passion fueled letters and poems on behalf of my friends for their various interests, but to date cannot do the same for myself.
But I was pondering over what you said of the whole legacy bit today(even voiced it to my hubby) and I must say your idea sounds commendable. Who knows perhaps unknown to us,decades from now, our younger generations may actually benefit and cultivate their lives based on our experiences and how we dealt with various struggles!