... become less stronger than before. So I use a opportunistic way to face the later English tests, and I pay less...
You'd better stop being an opportunist. You had better give up the opportunistic mindset.
.... (利用時機謀取私利) speculate; seize a chance to seek private gain; be opportunistic: 投機革命 join the revolution in order to seek personal gains 2. (見解相同) congenial...