We often make the mistake that friends or partners take away bad things. I've heard a woman describe how she can fall into her husbands arms after a long day and all the stress melts away. The subtly, kinda like watching Harry Potter to watch a movie vs doing it to worship satan, is that relationships should add good things to us, not take away bad ones. When we do it that way, we become dependent on the other person to fix us all the time and it becomes very dramatic, with high highs and low lows. Either you're what they call codependent or a leech on one side or the other. Either way, it's not conducive to overall well-being.
What you might notice is people in their high state, they feel good about themselves (i.e., self esteem) now that they have a place to throw their garbage. But I don't think overall, one should be seen as overly more happy in a healthy, long term relationship. Its an even keel with companionship added, not loneliness taken away.