Question: When asking around, I've never heard anyone agree that a young, healthy person should end their life by suicide. But I also don't know what reason there is for that consensus. 

Did Buddha teach anything regarding what makes life worth living?

Answer: 
Have you been to see a doctor about this? Depression can cause life to lack appeal. Why is life worth living is one of those questions that cannot be answered in words, it's an inner feeling that doesn't need an explanation that most have felt at some point. It's a sign of good health to have a passion for life. 

If whatever is causing you to feel that life is bleak changes, as it inevitably will, a passion for life can automatically emerge in you.

Life and death are two aspects of the same movement. By dying, the Buddhist would say, you don't really escape, for your return to life is guaranteed. Whether it is life as a human or not is another matter. So, what else is left if suicide doesn't improve things?

Given that life and death are one continuous movement, ever occurring, it makes sense to learn to live and learn to die.

Living in misery and dying in misery are common but not necessary.

Get tested for depression, and perhaps meditate with a good teacher in a monastery. The compassionate surroundings may trigger a change towards joie de vivre in you.
This [Scientific American article](http://www.scientificamerican.com/article/is-mindfulness-good-medicine/) describes some of the benefits of mindfulness:

> 
> As a remedy for depression and anxiety, mindfulness meditation may
>  help patients let go of negative thoughts instead of obsessing over
>  them. Training people to experience the present, rather than reviewing
>  the past or contemplating the future, may help keep the mind out of a
>  depressive or anxious loop.
> 
> 
> 

If you have thoughts that are repeating in a loop, perhaps you are focusing on those thoughts, intentionally or unintentionally, and as suggested above mindfulness meditation may be a solution.

You may read [A Guided Meditation](http://www.accesstoinsight.org/lib/authors/thanissaro/guided.html) by Thanissaro Bhikkhu to understand how to practise mindfulness meditation. If [The Five Hindrances](http://en.wikipedia.org/wiki/Five_hindrances) to practice disturb you, you can find the antidotes in [this essay](http://www.budsas.org/ebud/ebmed051.htm) by Ajahn Brahmavamso.

**What is the purpose of life? Well, the purpose of life is to experience true happiness.** That's one way to look at it. From the Thanissaro essay:

> 
> Then bring your thoughts back to the present. **If you want true
>  happiness, you have to find it in the present**, for the past is gone
>  and the future is an uncertainty. So you have to dig down into the
>  present. What do you have right here? You've got the body, sitting
>  here and breathing. And you've got the mind, thinking and aware. So
>  bring all these things together. Think about the breath and then be
>  aware of the breath as it comes in and goes out. Keeping your thoughts
>  directed to the breath: that's mindfulness. Being aware of the breath
>  as it comes in and out: that's alertness. Keep those two aspects of
>  the mind together. If you want, you can use a meditation word to
>  strengthen your mindfulness. Try "Buddho," which means "awake." Think
>  "bud-" with the in-breath, "dho" with the out.
> 
> 
> Try to breathe as comfortably as possible. **A very concrete way of
>  learning how to provide for your own happiness in the immediate
>  present** — and at the same time, strengthening your alertness — is to
>  let yourself breathe in a way that's comfortable.
> 
> 
> 

And what to do when your negative thoughts come back over and over to disturb you? The essay continues:

> 
> **If your mind wanders off, gently bring it right back. If it wanders
>  off ten times, a hundred times, bring it back ten times, a hundred
>  times. Don't give in.** This quality is called ardency. In other words,
>  as soon as you realize that the mind has slipped away, you bring it
>  right back. You don't spend time aimlessly sniffing at the flowers,
>  looking at the sky, or listening to the birds. You've got work to do:
>  work in learning how to breathe comfortably, how to let the mind
>  settle down in a good space here in the present moment.
> 
> 
>