1、然而，很可惜的是…
however, it is a pity that 从句
例：然而，很可惜的是他总是临时抱佛脚。
however, it is a pity that he should always cram at the eleventh hour.
2、换言之…
in other words=to put it differently
例：换言之，我会尽最大的努力达成我的目标。
in other words, i will try my best to attain (gain, live up to) my goal.
3、别人可能认为这是事实，但我不是。我认为…
it may be true as assumed by others, but i don't. i believe that 从句
例：别人可能认为这是事实，但我不是。我认为只要有坚定的决心和意志，胜利终究会属于你的。
it may be true as assumed by others, but i don't. i believe that if you have strong determination and perseverance, the success will certainly come to you in the end.
4、从此之后，我发现…
ever since then, i have found that 从句
例：从此之后，我发现微笑是面对生活中任何挫折的最佳方式。
ever since then, i have found smile is the best way to avoid any possible conflicts in our daily lives.