Why use harmony and not the word balance. Actually the word doesn't matter, because you always give your own interpretation and definition to a word. Sometimes that happens very intuitively or because that's how you learned the word.
For me, however, there is a difference. Balance makes me think of how life should always be balanced. Equal amounts of rest, equal amounts of busyness, equal amounts of time spent working or relaxing. There almost “should” be a balance in this day, in this week. Like being on a scale that otherwise drops to one side. And that doesn't feel appropriate for what I'm doing.
Perhaps not strange if you look at the definition of the word balance:
ba-lance (the; f(m); plural: plural: balances)
1 two-armed balance: to tip the balance to decide
2 balance: to be in balance in equilibrium to be out of balance out of balance
3 (bookkeeping) overview of the values of a company's assets, liabilities and equity on a given date: draw up the balance sheet calculate the result of his work (also figuratively)
source: Van Dale

Sometimes life feels super light and nice and sometimes life demands a little more of you than you would like. It's definitely important to recognize and see that so you can decide what you want to do with it. Sometimes there is no other way and you are using a lot of your energy. Then it's nice to give a little more time to silence and rest after such a period, so you can recover. But there are also people who just love to work hard for a period of time. There is nothing wrong with this if afterwards there is a period for rest and recovery. Finding harmony in life then is actually what it is all about.
It even feels a little like music.
In a very energetic piece of music or song, a quiet violin or piano moment can actually sound wonderful and stand out, giving time to breathe, to then continue on energetically. Or the seasons we have in nature, within which there is not always a perfect balance. But if we look at the whole of the different seasons, there is (normally) a beautiful harmony between spring, summer, autumn and winter which allows nature to keep itself alive very nicely.
Look also at the definition of this word:
har-mo-ny (the; f; plural: harmonies)
1 agreement: living in harmony in good terms, without conflict
2 (muziek) (music) pleasant-sounding union of tones
3 music ensemble playing wind and percussion instruments
source: Van Dale
Beautiful here are the words “in tune” and “union of tones.” It is tuning in each time to what life is asking of you at that moment, what you can give and what you need. Because it can be hard to balance everything in your life perfectly. But realizing what is there now and acknowledging what you need gives more peace and beautiful harmony in life. And that fits best with what I offer. Looking at you as a unique human being with your own desires and needs at this particular time.