1.1. I will feel better if I get it off my chest.
1.2. I will feel better if I have it over and done with.
2.1. You shouldn't take things so much to heart, he acted for the best.
2.2. Don't let it worry you, he acted for the best.
3.1. He complimented us on our success.
3.2. He congratulated us on our success. But the meaning here is slightly different. To congratulate doesn't imply to compliment; i.e., your work is stellar.
4.1. There was nothing original about it, in fact it was quite commonplace.
4.2. There was nothing original about it, in fact it was quite ordinary.
5.1. It’s a very controversial matter.
5.2. It’s very disputable matter. It carries a slightly different meaning, and I can't seem to put my finger on what that difference is exactly. Sorry.
6.1. He took infinite pains with his work.
6.2. He took great pains with his works. But infinite means immeasurably great.
Student or Learner