Career mode - running out of stamina

My 1st career run was heavyweight so I relied on my right hook. By the later rounds was always out of stamina with my opponent at 80%.

I thought maybe it’s a heavyweight thing so I moved down to lightweight- still wanting to KO people. The problem seems to be me throwing power shots all day long. At least that’s what I believe it is.

Does anyone have tips for me to better conserve stamina? Late game a lot of the fights go the distance and I end up slept by a good body shot lol

Thanks you in advanced - I’m lowkey buns

Edit: max stamina stats and conditioning around 80 usually if that matters. Still running out early on