如果你后悔没有好好学习英语，你可以说：
"I regret not having studied Engpsh more dipgently."
"I wish I had put more effort into learning Engpsh."
"I regret not taking advantage of the opportunity to learn Engpsh when I had the chance."
学好一门语言需要时间和努力，但是如果你愿意，你还是可以继续努力学习英语的。不要放弃，加油！