It's difficult to avoid them, but you can obviously make an insurances against some undesirable consequences, like house fire or illness.

Also keep a buffer of money to solve sudden stuff. Like, don't travel without having enough cash to get a return ticket, or if you rely on a car, you should always have enough money to make a down payment for a new one when it inevitably breaks.

In general you shouldn't have to be afraid of irreversible consequences. You have to break an egg to make a cake. Changes are most often for the better.

Some things are obviously more serious than others and sometimes you just can't know everything up front. Like having a child. That's a leap of faith that you just have to do if you want to. Changing jobs can also be nerve wrecking, but you can probably insure your income or make savings in case things don't work out.

Is there anything in particular you'd like to be able to undo?