3 ideas
A stone or connected group lives only as long as it has at least one liberty, meaning an empty point directly adjacent to it along the lines. When the opponent fills the last liberty the whole group is captured and removed at once. So a group's safety is measured by counting its breathing spaces, and so is the speed of any capturing race.
Before each move, estimate the territory you already hold securely and set it against what a contested area could add or cost. If the count shows you are ahead, take solid, simplifying moves. If it shows you are behind, you must accept risk and play for the uncertain areas. A move's value comes from its effect on this running count, not from how aggressive it looks.
A fight is worth starting only if its likely gain in territory or safety exceeds the cost of weakening your own groups and letting the opponent answer with profitable moves. Picking a fight you cannot win, or one that wins less than a quiet move elsewhere, loses points even when it succeeds locally. Knowing when to decline or abandon a fight is therefore as central to strength as tactical reading.