who must decide what to achieve and in what direction to aim your life这整句话是the one的定语从句；
what to achieve and in what direction to aim your life这整句是decide的宾语从句；
what to achieve 和 in what direction to aim your life是并列的,
理论上应该是decide to achieve what 和decide to aim ur life in what direction,因为是从句,对“what”做了一个宾语前置,
直译：你就是那个必须决定要取得什么和决定你人生目标取得方向的人,
中文地道一点应该算是：你必须决定你的人生目标和取得目标的方式.