Learn English – better expression for “not all roses”

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Is there a better expression for "not all roses"?
"Not all roses" sounds a bit cliched. This is for my personal history statement.

Eg: Once the design was complete, I thought the experiments would go smooth. Contrary to my expectation, the next step was ____________________ (not all roses).

Best Answer

To keep parallelism with the previous sentence, "rough going."