Whilst your story, particularly novels, should have twists and turns, it must still end up somewhere. Does your ending have punch? Don’t let your tale peter out. The ending should be satisfactory (notice not necessarily happy) and should seem natural for your story.
Are you keeping your readers guessing? Twists and turns shouldn’t be obvious. Part of the fun of reading is trying to second guess the author and not always guessing correctly!
Achievements and Directions
Does your character know what they must achieve? Do they care enough? If they don’t, your readers won’t care either and your story will sag. Is your character doing everything they can to get to that point? Commitment from the reader demands commitment from the character/author in the first place.
Do you know in which direction your story is going in? Any tangents off the main plot should be ones you want, not ones you accidentally get into. They should strengthen the story too.
Variety is the spice of (writing) life
Have a list of things to do, deadlines to meet, it keeps your writing varied and meeting deadlines is always good practice. It is what professionals do after all.
Vary your themes for interest. Vary the way you share those themes - novels, short stories, radio scripts… Vary your style too. You need a mixture of long and short sentences and paragraphs, which can be used to help pace too.
Vary what you read - fiction, non-fiction, in your genre and outside it. Not only is it more interesting for your reading life, you’ll be influenced by good writing from a variety of sources, which is bound to help your work.