By oneself; indicates doing something without relying on others, by one's own effort or in person.
宿題は自分でやりなさい。
Do your homework yourself.
彼は自分で問題を解決した。
He solved the problem by himself.
もし時間があれば、自分で駅まで行ってみます。
If I have time, I'll go to the station myself.