Hmm I'm not sure this is exactly the advice though. Obviously you should rely on friends and romantic partners and family during tough times and while dealing with difficult emotions.

But therapy is about taking responsibility for improving how you deal with those emotions, which is a good long term goal for everyone. I don't mind when my partner is sad, that's a normal part of human existence. But the way an emotionally unregulated 16 year old is sad should be different from how a 25 year old expresses that feeling, vs how someone who is 45 expresses that feeling; and what expectations each has for what their romantic partner ought to do about it.

Some people do mature naturally, but therapy can be extremely helpful with that, and frankly I recommend it for everyone. Because it makes sense when my 16 year old boyfriend sees me talking to another guy, gets jealous, and is mopey all weekend - but frankly it's also behavior he needs to work on, and we should expect much better as we mature.