Purpose of life
Short answer: Survive and reproduce.

Everyone including you and me have to die eventually. The purpose of our lives is merely to survive and reproduce.

For the surviving part, everyone want to live as long as possible in the healthy body. Diets, lifestyle and they way we live our life through our concepts. We are focusing on the psychological part. One of the best ways to achieve health and longevity is to be happy and relax. We are focusing on the psychological relaxation part here. One of the ways to achieve this is to learn to relax your body to the max through concepts, which can be enhanced through meditation.

Relax
Stress is one of the main psychological factors for our ageing and disease, and to reduce stress is to relax. Now the main concept. Since we have to die eventually no matter what we do, we have to let go of everything eventually. If you are able to let go of everything, you will be able to go into the deepest level of relaxation, which is the total freedom from troubles, everything will go very smoothly, and you will get the ultimate happiness and peace.

Happiness
There are different types of happiness actually, but it's hard to express easily. Most of the happiness people are having today depends on the external factors, which are impermanent. You will need to constantly get the things you want in order to get the happiness, and there are attachments involved which ultimately lead to suffering (for example, you are happy because you are rich, but this makes you attach to money. If anything happens threaten you to lose all your money, which is your source of happiness, you will be worried and won't be having the happiness you thought money will bring you.

The second type of happiness, which we are focusing here, does not depends on the external factor, which is the constant happiness without worried. This type of happiness comes from within you, which can be achieved through practicing of good concepts from moment to moment. For example, gratitude is one of the ways to achieve this type of happiness.

However, it's very hard to let go of the attachments in our daily lives which give us not ever-lasting happiness. One of the factors is because this is the easy way of living without the need to practice anything. But ultimately, due to attachments, this will eventually lead to suffering. Another thing is even though there are suffering involved, people are so enticed to the temporary happiness at that moment.

What to do in the present moment
Short answer: observe, relax and adapt.

Although we all have to die in the end, we still have to live our current life to the best, and the best way to live our life is still through relaxation, and observation. If you are able to let go of everything and relax your body to the max, what are you going to do everyday? The answer is to be gratitude that you still have your consciousness until you die, you can still interact with the universe and the environment through your senses like see through your eyes, hear through your ears, breath through your nose and think through your mind.

So how to we use our consciousness in the present moment, before we die eventually? The answer is to observe, relax and adapt. Observe your surrounding through your senses and adapt through your mind. One of the thing to note here is every action we do root from our mind (if you observe yourself carefully, the environment or concepts tell our body / mind to take a certain action).

The best way to live your current life is to be healthy and happy (happiness which does not depend on the attachments and clinging). To be happy, you need to relax, and to be healthy, you need to have the correct diet, lifestyle and concepts. In order to achieve the best health you can get is through knowledge and practice, and to get the knowledge for you to live to your best, you need to observe through through your senses and then adapt to the current universe and the environment needs (the current society).

Not a single person is identical with another, and many people have different concepts from each other. These different concepts root from different experiences they have, which they observe the environment through their senses, and these concepts lead to all the different actions they would take.

In order to take the correct actions (which are the actions which lead to our better health and happiness), you have to observe your body and the surrounding, in the deep relaxation state. Then you will need to form a concept carefully (majority is through the assist of our subconscious mind) and then live with the concepts you've formed and strengthen them through your daily lives.

Conclusion
Short answer: Let go (relax), be gratitude, observe and adapt.

Life is complicated, so is the article above. To summarise, since we've to die eventually, we should learn to let go of all the attachments (which will lead to deep relaxation).

But we still have the consciousness to live our current life in the present moment, and we should be gratitude for that.

We then use our consciousness to observe the environment and our body through our senses and then adapt ourselves to the need of your body and the universe.