PHRASAL VERB 埋头苦干；孜孜不倦地做 If you plug away, you keep trying very hard to do something or achieve something even though you find it difficult. 埋头苦干；孜孜不倦地做
My confidence is still there and I'll just keep plugging away. [VERBPREP.]
我仍有信心，会继续坚持不懈。
SYN slog away, labour, toil away, grind away [informal]