How do I handle office politics that drain my energy?

You came to do the work, and instead you spend your days protecting it from people who want to pick it apart. That is exhausting in a way that has nothing to do with the work itself. It drains a different kind of energy, and it is real. Some defending is part of any job. But if it has become most of your day, something is out of balance. Look honestly at where the energy goes. Some battles are worth it. Many are just noise from people who need to feel involved. Learn to tell them apart, and stop feeding the ones that don't matter. Try this: explain your work once, clearly, and then let it stand. You do not owe endless justification to everyone with an opinion. Save your strength for the work itself. That is what you are actually here for, and it is what will outlast the politics.