Think of your own situation - if you were spending more that you earned and going into increasing debt, is the answer to up your spending?
Countries aren't people.
However, lets say I'm building a house. The budget has increased from £100k to £200k.
By your measure I should just have stopped when I started to run out of money at £80k and then vastly reduced costs to keep the house to the £100k budget.
Because of the cost cutting it now has two less bedrooms, only one bathroom, no conservatory and a budget kitchen. I sell the house and realise £100k of profit. Which is great.
However lets say instead of cost cutting I take on £100k of debt. I'm able to finish the house to the original specification with the conservatory, granite worktops and 3 bathrooms. I can then sell the completed house for £500k.
By taking on debt I have expanded my economy, created more work for the people I am employing and have a return back into my own economy later on.