You can reduce the number of improvements that are costing you a fortune. Virtual Reality Center, for example, cost 5/month.
(These should never be built IMO as the cost is not worth the benefit)
You can also reduce your spending level. If you have no trade revenu, the highest spending you can sustain without loosing money is somewhere between 60 and 70 percent. Note that if you build all the special production buildings (manufacturing capital, hyperion center, etc.) on the same planet, the planet in question will be in deficit much sooner than 60% spending.