•Keep in mind (idiom) –
To remember and think of.
1.Students will need to keep it in mind that classes begin an hour earlier than normal on Monday.
2.I'll keep your advice in mind.
•Step forward (phrasal verb) -
To offer to provide or do something, or to help with something.
1.No one has yet stepped forward to claim responsibility for the attack.
2.At the last minute another company stepped forward with a bid.
•On one's mettle (idiom) -
If one is on his mettle, he is ready to try as hard as possible because his abilities are being tested.
1.We'll have to be on our mettle from the start.
2.Both players were on their mettle in the final round.
•A thorn in one's flesh/side (idiom) -
A constant or persistent cause of annoyance, pain, frustration, or trouble.
1.This problem is a thorn in my flesh. I wish I had a solution for it.
2.She's a real thorn in his side.
•Plough a lone/lonely furrow (idiom) -
To do something by one and in one's own way, without any help or support from others.（獨自行動，孤軍作戰）
1.She has had to plough a lone furrow in her pursuit of reform.
2. It seems that he was something of an original thinker, ploughing a lonely furrow.