The best plan with HIV is not to get infected in the 1st place. To prevent infection with HIV:

• Never have unsafe sex: always use a condom!
• Don’t be exposed to infected blood (through sharing things like drug injections, or blades, tattoos).
• Make sure that babies are not infected by their mothers.

To be safe, you should assume that everyone could be HIV+. You can't tell if someone is infected by how they look (because everyone looks well for many years after being infected). The person may not even know that they are infected or they may not tell you.

And remember that being in a steady relationship doesn’t guarantee anything. Some people got HIV from their steady partners who were unfaithful. So it’s a good idea to use condoms in any relationship.