I wonder if it's painful to grow legs and feet and lose a tail, to go from being a tadpole to being a bullfrog. Because it certainly seems painful to go through a human transformation. Do tadpoles miss their tails and wish they had them back? Because we people seem to have a hard time with changes of all kinds. We (adults at least) wish for what we used to have - youth and beauty, agility, a particular sense of family, innocence, our best friend, fun times in the neighborhood, our former teacher or mentor, security, and (as they say on TV) much, much more. We miss people, we miss things, we miss times from our old lives. This is natural of a species that forms emotional bonds, that lives in community. We can't expect to become attached, experience happiness and belonging and then just change things - leave friends, lose people to death or moving away, experience all kinds of losses and changes - and not feel bad about it.
Still, we are called to be transformed by the Gospel and to be willing to leave people and things behind (see, the calling of the disciples as well as Luke 9:59-62 - 'let the dead bury the dead, he who looks back is not fit for the kingdom of God,' etc.) And just as importantly, we are called into a new community, not to be solitary. And through this new community we and the world around us will be transformed.
But there is loss in transformation. Sometimes the loss is positive - losing one's emotional baggage that keeps one mired in dysfunction, or losing those extra pounds that endanger our health. But even then, one has become used to the way things were - some who lose those extra pounds then need to figure out who they are again, to deal with other people finding them attractive, say, or working to gain self-confidence in public. Even when what one leaves behind is negative, it was often comfortable, known, dealable-with. We love our routines, even when they become deep ruts. Remember the Israelites who wanted to go back to Egypt after they had escaped Pharaoh. They may have been slaves in Egypt, but the food (cucumbers! melons! garlic and leeks!) was a lot better than what they were getting in the wilderness.
But we are always in the process of transformation. Some of it welcome, much of it not. We are losing our rough edges as we move through life; we are losing our narrow view as we are exposed to more and more (even things we don't want to be exposed to). We are preparing to take on new life - becoming partners, parents and grandparents; becoming generous; becoming wise; becoming peaceful; becoming trusting - and that often means making way for that new life by shedding part of the old. Shedding mistrust, anxiety, ignorance, tight-fistedness and hard-heartedness, shedding living alone with no one to consider or care for. We are always in the process of transformation, in the process of "becoming." And like the ugly duckling, we may not even realize that what we are becoming is beautiful.