Making optical networks more efficient and reliable requires further automation of the optical layer. In this context, we propose a closed control loop that automatically performs fine frequency adjustments of the subchannels of superchannels to maintain optimal performance despite time-dependent impairments, thus achieving three main goals. At design, our scheme reduces the need for margins and guard-bands dedicated to spectrum-related impairments such as filter or channel detunings. This allows for a more efficient network at deployment. Then, during operation, the quality of transmission (QoT) of each subchannel is maximized to make the superchannel more resilient to any kind of soft failure, thus improving network resilience. Finally, considering the elastic network paradigm, performance improvements can be converted into significant capacity upgrades. We demonstrate the ability of our solution to achieve these three goals with split-step Fourier simulations. For a four-subchannel superchannel, we demonstrate robustness to +/- 2 GHz frequency detunings and gains of up to 3.7 dB in quality of transmission.