Given what it does to mitochondria (complex I inhibition), https://pubmed.ncbi.nlm.nih.gov/30619086/ it's not surprising that it feels draining and makes exercise difficult. I've also seen a couple of studies indicating that it makes building muscle difficult - and that's not surprising, given that reduced mitochondrial activity means less reactive oxygen species from exercise.

I've gone with Berberine instead (evenings only). Similar inhibition, but also a PCSK9 inhibitor (better scavenging of small dense LDL by the liver).