When writing a short story, how do I make sure I'm not rambling?

Sometimes I go and and on about something (like it's stream of consciousness), and it makes the whole story tedious to read. But other times I don't have enough details which makes the pace too fast. How do I make sure my writing is straight forward but still filled with colorful sensory details and characterization? MaMore more action and less thoughts that don't relate to the plot? thanks in advance :)