Sounds like you may need to change your approach. The game is challenging, but with the right strategy each stage is beatable even without synergies.
Analysing the charts to see where you might be using too much time can help. You should also look at the resources remaining at the end of your lifespan, and make sure you're not left with anything that doesn't contribute towards the goal. Replaying earlier levels for bonus synergies also helps. Good luck!