Like true love, I somewhat believe this can exist, but most of the people who talk like this are in a codependent relationship. It's just extremely unlikely that a person you're seeing romantically is also interested in all the other things you've got going on. They should support you in your endeavors in general, but often in the way parents might ("ya winning son"?).

Instead, the best relationship for most people will not be all encompassing. Your partner will love you for you and encourage you, will know what you're up to and keep track, but will also have areas and interests that you aren't into. For me, a lot of my growth has come from the areas where partners are into things I'm not: I don't change to be like them, but through their eyes I learn to see things in new ways (while still liking what I like). It can go too far in the other direction - but for most people having parts of your life your partner is not very involved in is a sign of maturity and strength. A strong relationship is a base from which you can set out into the world on your own terms, free to return to that relationship in the future.