There is an old saying "well begun is half done"-'tis a bad one. I would use instead-Not begun at all 'til half done.
John KeatsTo Hope "When by my solitary hearth I sit, And hateful thoughts enwrap my soul in gloom; When no fair dreams before my 'mind's eye' flit, And the bare heath of life presents no bloom; Sweet Hope, ethereal balm upon me shed, And wave thy silver pinions o'er my head.
John Keats