SP Rythin's rules
If you played wisely and had a good timing during the first two hundred years, you would probably create a really kickass nation, capable to vassalize everyone in Europe not ruining its economy at all. To prevent this situation and to enjoy the troubles till the real end in 1819 I gathered a bunch of rules you should abide - they backward you a bit, so that AI could match you.
1. Never attack without a CB.
2. Never take more than two provinces in a peace treaty (preferably only one).
3. Never force-vassalize any country that has 3+ provinces.
4. Never research infra after 6th level.
5. Never diploannex before 50 years of vassalization.
6. Never dow countries for gamey reasons (fight only with those countries that normally real medieval/baroque monarch would fight with).
7. Stick to your historical area of colonization.
8. Always choose the hardest path (take Hussites as Bohemia, try to change to reformed as France, etc.)
9. Never exchange discoveries.