Use the right tool for the job. If the job requires precise control of memory, FP is not the right tool. If the job requires precise control of sequence, FP not the right tool. (Yes, it's a tool that could be made to work, but you're fighting the tool rather than working with it.) If the job requires precise control of timing, lazy languages are the wrong tool.

This does not mean that there is anything wrong with FP or with lazy languages. They're just not the right tool for all purposes. When they're not the right tool, don't use them for that.