Edge the lawn
Trim your lawn edges with long-handled shears or a motorised edge trimmer. When the grass is growing rapidly you may need to do this every time you mow. Be careful not to cut into the turf as you work down the line. The task is easier and the finish will be cleaner if the turf edge is above border soil level and has a vertical face. Edged lawns looks very neat but it also stops the grass growing into the border and becoming a weeding issue.