Here are the suggested words to fill in the blanks:

1. (7) **advice**
2. (8) **wisely**
3. (9) **positive**
4. (10) **lifetime**

So the completed text would be:

"___, you support one another and make a big difference. They can listen, offer (7) **advice**, or simply be there for each other. Having friends who are kind and understanding can boost a teenager's confidence. However, it’s also important to choose friends (8) **wisely**. Sometimes, negative friendships can lead to peer pressure. Teens should surround themselves with friends who encourage (9) **positive** behavior and healthy choices. By building strong friendships, teenagers can create a support network that lasts a (10) **lifetime**."