Material stuff will not make us as happy as we thought it would, nor will marriage (on the long-run). Humans are very bad at identifying what will make them happy.
On the other hand, something that will work is gratefulness, random acts of kindness, or making new social connections.
It happens often that our minds' strongest intuitions are wrong, so we will follow an idea and realise after that it didn't have as much impact as we thought it would. These bias are very common but once you know they exist, you can avoid them