I used to wonder the same thing as I was the healthiest one of my friends, yet was breaking out uncontrollably. Here is my skin blog on what I did (and continue to do) to have clear skin. Note, the supplements are definitely the number one key to healing. Best of luck, and please reach out with any questions. 🙂
http://www.acne.org/messageboard/blogs/entry/32202-how-to-heal/
The predominant factor is genetics. Some people will hardly see a sign of acne in their life, even if their hygiene isn't all that great. Others struggle with it for decades.
Of course, just because it's in your DNA doesn't mean there isn't a solution. If you whittle down the options, you'll find something that works. Process of elimination, basically.
It's always worth seeing a dermatologist, especially if healthy lifestyle habits and various OTC treatments prove unsuccessful.
Ones idea of eating healthy may be anothers idea of junk food. You could be eating something your allergic to, it could be the wrong face wash, maybe youre over exfoliating, or not enough. Maybe your waters harsh, or youre low in vitamin d. Maybe you need to eliminate dairy, or gluten, we dont know. We dont know how you live! Everyone is going to offer their advice and mine is this: go see a doctor and dermatologist. Get some tests done
A couple people mentioned the fact that it's most likely due to genetics and I think so too. I found out recently that there are more than a few people in my family who have had acne in the past. Honestly, it makes me feel resentful towards them for passing the genes down to me. I don't want to have any children because of the fact that I'm afraid I'll pass down the genes of having skin issues. Hopefully we will all find a solution for our skin issues soon. Everybody's skin is different which makes it hard to pin point any single solution for each person. Life. I wish it was easier than this.
No one in my family has ever suffered from acne. As a matter of fact, they all have fantastic looking skin and so did I until about 2 years ago and than I finally cured it. It is most likely something going on in your gut. Taking supplements to reduce gut bacteria is what cured my skin.