How can a nonprofit maintain net assets if depreciation expense is 25% of overall budget?

My nonprofit went into real estate by purchasing a building that dwarfs the core c3 on the balance sheet. So depreciation/amortization expense is killing me. It seems like the only way for me to maintain net assets is to have a surplus greater than depr/amort and then lock it up in cash (or other assets). That's very onerous. Otherwise my net assets will eventually fall to zero and below....Anyone with experience dealing with this?