As answered by Claire J. Vannette…
It’s like having multiple close friends. It’s like having multiple siblings. It’s like having multiple parents. It’s like having multiple kids. It’s like having multiple lovers sequentially, except you have them concurrently.
Recall all the joys and challenges of your first sweetheart, and all the joys and challenges of your second sweetheart, and imagine experiencing those simultaneously. When things are good in all of your relationships, life is amazing. When things are crappy in all of your relationships, life sucks.
The nonmonogamy-is-hard meme pops up pretty frequently, and it just doesn’t reflect my experience. Monogamy was hard. It took serious effort to tamp down my affection and desire for all the lovable and desirable people other than my current partner. I sometimes did not succeed, and then I had a steaming pile of guilt to deal with, which usually prompted me to end the ostensibly-monogamous relationship and mope for a while about my dysfunction. Cheating was hard. Now that I exclusively date people who are cool with me dating other people, my life is much, much simpler.
There are certainly logistical challenges involved in allocating your time to multiple people, but everyone deals with that, assuming they have multiple people they wish to spend time with and multiple demands on their time. When I compare my schedule to my monogamous parents’ schedule, mine is much simpler. They have my little sisters to deal with, so they run from archery practice to school recitals to sleepovers to doctors’ appointments. They go to temple, they hang out with their friends, they travel for work, and they do home improvements. Juggling all that is hard. Keeping track of a few dates a week is a piece of cake. Google Calendar, man. Technology works wonders.