1. It was a red-letter day for me, the day I was elected president of the company! < a very good, important day.
2. Necessity is the mother of invention.
3. I don't really trust Erica. She tends to run with the hare and hunt with the hounds. < she takes the easier route; untrustworthy.
4. You can't make a silk purse out of a sow's ear! < it's impossible to do something well without the right settings, or materials.
5. Look before you leap! < be careful and don't take chances! (a leap is a big jump)
6. He who hesitates is lost. < delay or indecision may have catastrophic consequences.
7. He who sups with the devil should have a long spoon. < If you mix/eat with evil people, you need to keep your distance.
8. Beauty is in the eye of the beholder. < people see beauty in different ways according to their own interpretations.
9. Pride comes before a fall. < said as a warning to people who are very proud, that they could come to disaster.
10. You scratch my back and I'll scratch your back. < If you do me a favour or help me, I'll do the same for you.
11. Sticks and stones may break my bones, but words will never hurt/harm me. < being physically attacked will damage me, but insult me all you like, I don't care.
12. Variety is the spice of life. < the more changes you enjoy in life, the happier you are.
13. (he's a) Jack of all trades, master of none. < if he tries to do lots of different things he is probably not very good at any of them.
14. Marry in haste; repent at leisure. < If you marry quickly, without careful consideration, you'll have plenty of time, when married, to regret it.
15. Money talks. < if have a lot of money, you can exert power and influence.
16. Let's bury the hatchet. < let's forget our past quarrels and make peace with each other. (a hatchet is a type of small axe)
17. Live and let live. < live your own life and don't interfere with the lives of others. (incidentally, "Live and Let Die" is just the name of a James Bond film!
18. Waste not, want not. < if you are careful or thrifty, you will be better off or richer. (thrift means careful not to waste anything)
19. When the cat's away the mice will play. < when the person in authority is absent, the people he rules or manages tend to do what they like.
20. Mighty oaks from little acorns grow. < said to encourage someone who is starting from scratch - start small, but later you may become very big and important.