It means to act with the certainty that what you do matters. You cannot say that what has happened was not supposed to happen. You cannot say the results were not what was supposed to be. That is not up to you. It is up to you to decide what you will do with this.
You have been put in a circumstance by a Being who is all kind, all truth, and all just. You may not be in the circumstance that you want, and you are most certainly not in the circumstance that enables you to retire passively and say “now things have reached that ultimate perfection G-d was hoping for”. You can know that you are precisely where you are meant to be. The challenges and victories that surround you are the challenges and victory G-d wanted you to face right now.
You can also know that you are limited in the actions you can take to meet these challenges. While you may feel like acting without restraint or without respect for those who think differently, you can know without reservation that those actions are not the Will of G-d. G-d does not operate without restraint and does not operate without respect, care or interest for the greater purpose of every living being.
What does it mean to believe in G-d in 2021? It means to act with purpose to act with respect and to act with understanding that we are where we are meant to be. We can move from here to make things better and we can act with the love, respect and care we were put in this world to offer.