Seichou Cheat de Nandemo Dekiru you ni Natta ga, Mushoku dake wa Yamerarenai you desu - Vol. 10 Ch. 39

[MangaDex]

 

[Moridin69]

Its good that protag boy is strong (well, decent anyway compared to MC OP-ness). MC needs to practice and learn to use less power so he can pace himself better. No need to use MAXIMUM EFFORT when a couple of lesser attacks will do and leave him with more energy.