DhP 77 One should advise and instruct [others], and prevent what is unwholesome; For one is dear to the virtuous, but to the unvirtuous, one is not dear.

DhP 78 Do not associate with harmful friends, do not associate with base people; one should associate with good friends, one should associate with best amongst people.

DhP 79 One who is joyous in Dhamma dwells at ease, with a clear and tranquil mind; In the Dhamma taught by the noble ones, the wise person always rejoices.

DhP 80 Irrigators direct the water, fletchers bend the arrow; Carpenters shape the wood, And the wise tame themselves.

Related Teachings:

Who to associate with (AN 3.26) - A man who associates with an inferior goes downhill, but associating with an equal, you will never decline; following the best, you will quickly rise up, so you should keep company with people better than you.

Somanassa sutta - Joy (ITI 37) - Endowed with two qualities, one can abide with abundant joy and ease - 1) by being moved on occasions that inspire a sense of urgency, and 2) by wisely striving when aroused with energy.