Yoga and meditation are akin to “Swiss army knives.” A Swiss army knife has different tools for different functions packed into a single unit. Yoga and meditation both have different components to help people improve their lives, and those components exist within each of the two disciplines.
One of a number of things that yoga focuses on is physical fitness. Yoga helps individuals improve their strength, flexibility, and body chemistry. Yoga can be combined with walking, light to medium cardio, and light to medium weight resistance training. But yoga in itself can be tailored such that it provides extreme cardio and aerobic conditioning when one moves within the various postures.
Meditation provides invaluable help to anyone seeking to improve their mental and emotional health and well-being. Beginning the practice of meditation requires that a person stick with it for a period of time even if they don't sense that they’re getting immediate benefits. This is the case because most of us aren't able to attain stillness of mind until we discipline ourselves to do so.
Those who meditate can improve their concentration, move away from distraction, and focus on character development if they choose to. They can both appreciate their own worthy acts and manage their egos such that they don't become obsessed with themselves.
Yoga and meditation can most certainly help individuals improve themselves. But the goal of self-improvement should be to benefit other people, other creatures, and the planet we inhabit. For that reason, those who practice both meditation and yoga should do so to develop the quality of compassion in themselves.