The phrase "full of pep" denotes energy, enthusiasm, and vivaciousness. Its antonyms would be words like sluggish, lethargic, lazy, and apathetic. When someone is not full of pep, they appear to lack motivation and vitality. Such a person may be seen as lacking ambition, drive, or passion. Being sluggish or apathetic can lead to a decline in productivity, and ultimately lead to poorer wellbeing. Thus, it is important to find ways to stay energized and enthusiastic to stay productive and maintain overall health. Endorphin-releasing activities like exercise, music, or socializing can help connect us to our inner selves and help us cultivate a positive outlook.