He's speaking up and asserting himself and doing things he enjoys.

他现在直言不讳、彰显自我，做着他喜欢做的事。

《柯林斯英汉双解大词典》

If your child has a problem with asserting himself or herself, you should NOT criticize the opinions that they express until they show that they are comfortable with asserting themselves.

如果你的孩子在表达自我上遇到问题，那么在他们能愉快地表达自我前，千万别批评他们的观点啊。

youdao

Phra Dhammachayo has refused to turn himself in, asserting that he suffers from diabetes and Turner syndrome, a chromosomal disorder.

拍·达马查育拒绝自首，声称自己患有糖尿病和特纳综合征，后者是一种和染色体有关的失调。

youdao

Meanwhile, Attorney General Alberto Gonzales defended himself Monday in an NBC interview, asserting that he had not misled Congress or the public when he declared that he had not participated in discussions or seen documents about the firings.

NPR: Gonzales Aide to Take Fifth Before Senate Panel

Many believe, as the Afghan president himself said this week, that he was simply asserting his country's sovereignty against meddling foreigners.

ECONOMIST: President Karzai threatens to join the Taliban

Yet he simultaneously claimed a huge retrospective dividend for himself from the privatised utilities (the windfall tax), asserting that this would have no impact on investment by these firms.

ECONOMIST: A disappointing start