In a large skillet cook onion, sweet pepper, carrot, celery, and garlic in hot oil until tender. Stir in fresh or undrained canned tomatoes, tomato paste, dried herbs (if using), sugar, water, salt, and pepper. Bring to boiling; reduce heat. Cover and simmer 30 minutes. If necessary, uncover and simmer 10 to 15 minutes more or to desired consistency; stir occasionally. Stir in fresh herbs, if using.
Meanwhile, cook spaghetti 10 to 12 minutes or until tender but still firm. Drain well. Serve with sauce.