自分の能力を

one's abilities

→ 自分
phrase Rare #40,659
one's abilities 自分の能力 means “one's own abilities,” and を marks it as the object of a verb. This phrase normally appears before a verb, such as 活用する (make use of) or 評価する (evaluate).
JA: 自分の能力を信じて、挑戦してみよう。
EN: Believe in your abilities and give it a try.

彼はよくできない自分の能力を最大限利用していないからだ

He doesn't do very well because he isn't making the most of his abilities.

彼は自分の能力を確信している

He is confident in his abilities.

せいぜい自分の能力を活用しなさい

Make the most of your abilities.

若者は自分の能力を正しく評価できないことが多い

Young people often fail to accurately assess their own abilities.