A dysthymia diagnosis is a validation that you live with a lower baseline mood than that of the average person. They associate the word "mild" with this, but that doesn't mean it's a mild condition. The real disruptor is its always-there nature and long-term persistence.
Aripiprazole seems like an unusual first-line treatment for dysthymia, especially if it's a standalone medication. This would normally be used as a low-dose add-on to an antidepressant. But then, I'm not a doctor, and I'm not familiar with your situation.
There's not really any predicting what you'll experience with it.
You could keep a medication journal with a record of start/stop dates, any changes in dosage, any positive or negative effects (and to what strength), any changes in mood etc. If you do this and need help tracking changes in mood, go to Google and look for a depression test you could take on a regular basis, maybe once every 7-to-10 days and record your scores (the Beck Depression Inventory is pretty thorough, if you don't mind its length).