All your actions are constantly graded by the inhabitants of your city. Their opinion about you is represented by two indicators - dissatisfaction and hope. They are partially related to each other - some actions that increase hope can cause dissatisfaction to drop. There are also activities that change only one indicator. You must keep watch that none of the indicators reach extremely low values.
The basic modifier is the problems that your colony is facing. The game always informs you about current troubles of your citizens. This enables you to see how much there are sick and/or wounded, hungry, homeless people.
The more problems and the greater their scale, the stronger is their impact on the indicators. Because of that you should try taking care of trouble at their early stage.
In case of food it is impossible to react immediately. This is caused by the time needed for obtaining unprocessed food. Luckily, a single day of hunger shouldn't cause serious problems. There are two reasons for a lack of food. The first one is the number of gathered food. In that case construct more hunters' huts and make sure they hire as many people as possible. The more workers, the greater the efficiency of building - so if you can, transfer some people to the huts. The second problem can be the number of prepared meals. The kitchen works only from 8:00 to 18:00, so the number of processed food is limited. In this case you should construct additional kitchen. If you decide to do that, you should combine the construction with feeding policy. Both kitchens are working independently, so each of them can create different types of meals. This will have positive impact on the dissatisfaction indicator.
As for the health, the situation is more complicated. Medical posts must be placed in heated zones, which means you can't place infinite number of them. Additionally, they have limited slots for patients and the healing time is long. In this case you should unlock and construct a care house that will take in terminally ill, freeing place in medical posts. You must also decide how the patients will be treated. It is better to introduce a law about radical therapy, making it possible for doctors to heal everything, even what is considered as incurable. In this case only people whose therapy failed or caused permanent health disorder will go to the care house.
Try to maintain temperature in the city. You should especially watch out for miners who are working far from the reactor. If the temperature will drop too far, the number of sick people will be too high for you to heal them all, causing a drop of the parameters. In that case you should provide a proper temperature only in one place in house or in the working place to reduce the risk of becoming sick.
Another modifier is various buildings that can be unlocked in the book of laws. These buildings can reduce the dissatisfaction. For example, fighting arena and the public house can provide entertainment to the citizens. You must have at least one building like that to secure dissatisfaction level.
The last thing that can impact dissatisfaction and hope is the book of laws. Each decision you make have a specific impact on both indicators. This aspect is described in detail in the subchapter "The book of laws".