Like-minded people associate together, as do birds of the same species. The early bird catches the worm. It's the straw that broke the camel's back. When the cat's away, the mice will play. Act when the opportunity presents itself.
All cats appear grey in the dark.
Under certain conditions, we all appear the same. Don't count your chickens before they hatch. Curiosity killed the cat. Too much curiosity can cause one to abandon caution and encounter unseen danger. One who associates with people of bad character or habit are likely to pick up bad attitdudes and habits.