I love making software run faster with the same resources, I love saving machines/hardware, etc.
On this topic I would recommend you a short paper about optimizations which focuses on how you should think about it to do it in the right way.
One we interesting part of the paper is:
"Won’t software with extra code path to measure timings be slower than the same software without that extra code path?
I like an answer that I heard Tom Kyte give once in response to this question.15 He estimated that the measurement intrusion effect of Oracle’s extensive performance instrumentation is negative 10% or less. 16 He went on to explain to a now-‐vexed questioner that the product is at least 10% faster now because of the knowledge that Oracle Corporation has gained from its performance instrumentation code, more than making up for any “overhead” the instrumentation might have caused."
I admire the Tom Kyte's answer. I want to point a finger at the face of all system administrators, CTO's, etc. - people turn on logs and your profile systems. They really help developers to optimize their code. Do not just blame them that the application sucks.
And if you want to read more check Baron Schwartz's bookshelf.