The opposite of "more second nature" could be "less accustomed", "unfamiliar", or "awkward". These antonyms suggest a lack of ease and comfort in performing a particular task or activity. When something feels less second nature, it may require extra concentration, effort, and practice. For example, using a new software program may feel awkward at first, but with time, it can become more second nature. Similarly, adjusting to a different work schedule or job responsibilities may initially feel less second nature, but eventually, it can become more familiar and comfortable. The antonyms remind us that developing a new habit or skill takes time and patience.