(OK, off the political soapbox and back to Torah... that's why you read this blog, I hope!)
The experience of shiras hayam was spiritually overwhelming and reached every single person - "ra'asa shifcha al hayam mah she'lo ra'ah Yechezkel ben Buzi". Yet, immediately afterwards Bnei Yisrael begin their travels with three days of no water, symbolic of Torah, and start complaining.
That seems to be the way life goes. Some days you are learning and davening and it feels like the shiras hayam. The next morning you wake up and mamesh nothing: davening passes without kavanah, you can't make it through the daf, you have no connection to ruchniyus, and so the day goes and maybe the next.
How to achieve a balance between the ratzo-v'shov going back and forth from gadlus hamochin to katnus hamochin is a real challenge and I don't have an answer myself. See the Ishbitzer who has an analysis of how the mitzvos given at Marah are a response, but I do not yet fully understand this torah.