The intermingling of universes is always a significant thing.
Dating and marriage take this to an extreme, I think, because significant others are a pretty big part of our worlds (or at least, they should be). Friendships too can be similarly extreme. Even a person on a street whom you simply pass becomes part of your universe for a brief moment.
Universes are made closer by sharing. Whether it’s time, experiences, or yourself, you must share something with the people with whom you wish to be closer. Is it worth it? Usually, yeah. Your universe expands, and so does theirs. Together, you grow, and hopefully improve.
As previously mentioned, with dating and marriage, it’s a lot more serious. All of your muchness, everything that is you, becomes attached with another, and the same happens to the significant other. this in particular is of import. If this is taken lightly, people can (and do) get hurt. People can be afraid of forever making that commitment, or maybe they’re just not interested in it altogether. Maybe they thought at the beginning that they were ready for it, but now, they don’t know. Maybe they were, but now they’re not.
In any case, tearing apart these intermingled universes is usually about as graceful as it sounds. It’s a bit unfortunate when it happens, but for some, it can be good. Personally, I think of people who aren’t in the best relationships as benefiting the most from this. (Here’s a website that will hopefully help if you’re in one of those.)
To finish, before you jump into anything serious where your universe will be intermingled with another significantly, think about it with care. Be like Ed Sheeran in his song “Dive”, questioning motives, intents, and whether it’s worth it. Or don’t, I guess. It’s your life, your universe. Take care of it.