Nike has one of the best slogans out there, truly. "Just Do it" can be a response to just about anything good.
Should I follow my dreams? "Just do it."
Should I pursue my passions? "Just do it."
I feel like God said to do this, should I do it? "Just do it!"
Throughout the Bible, there were many times when people "just did it" out of obedience, though they lacked understanding at the time.
Abraham took his only son, Isaac, up a mountain to sacrifice him at the Lord's command. He there saw the provision of the Lord burst through and redeem his son, providing a ram in the thicket to sacrifice in Isaac's place. This became an entry point for the then-future Messiah to redeem all of mankind (Genesis 22). Abraham didn't understand what God was doing, but he did it anyway.
Ruth left her own family, culture, and gods to follow her mother-in-law, Naomi, back to her hometown when all the men of the house had passed away. She was not obligated to look after or to help her. She did not know her act of sacrificial love would be recorded in history when she left everything to go with Naomi. She was unaware her willingness to obey whatever Naomi told her to do would position her to be the great (several times over) grandmother of Jesus (Matthew 1:5). She just did it.
When the disciples were told to go look for a donkey to borrow for their master, they did not understand they were fulfilling the prophesy of Zechariah 9:9 concerning the Messiah. They just did it anyway.
Bob bought a bag of apples and became a multimillionaire. He heard God's voice and just did what He said to do.