...what it leaves behind is hard - sings Dave Mustaine. And indeed, once you set your mind to the change its quite simple step to take.
What makes moving on hard are the things you might need to leave behind. Whether it's moving to another city, or even across the globe, or changing your habits it's not that complicated. For example, moving to another country you just need to find a place to stay, book the flight and pack your stuff (and maybe do some tedious paperwork, but that's just a technicality). Same with the habits: want to start living healthy? Just drop all the fat and sugar and leave the comfort of the couch and head to the gym.
But it's not easy to just leave those things behind. Change requires sacrifices, you need to let go of something to be able to move forward. It could be your friends and relatives to move to a new country or giving up your favourite foods to become more healthy. In general, it requires you to move away from your comfort zone.
Unfortunately, we can't take everything we like with us when we are moving forward. But there is always something new replacing those things if we are willing to give them a chance.