Initially, don't think of it as a lifelong commitment. When you wake up each morning, promise yourself to do your best to make healthy choices that day. Sure, you'll trip up occasionally, but the overarching theme of your choices will be healthy. I read somewhere that it take about 3 weeks to develop a new habit, so within a month, making healthy choices will be fairly routine and you won't even be thinking about it. Point is, take it a day at a time.