It is high time you _________ taking your health seriously and _________ exercising regularly.

• Complete Sentence: It is high time you started taking your health seriously and began exercising regularly.

• It is time/It is high time:
→ It is time/It is high time থাকলে আর এর পর subject বসলে subject - এরপরের verb টি past form হয়।

"It is high time you _______ taking your health seriously and _________ exercising regularly." বাক্যে,
→ এর শূন্যস্থানে verb হবে started এবং began.
→ কারণ, It is high time এর পরে subject – you এসেছে এবং তার পরে 'started' এবং 'began' verb হিসেবে এসেছে। 

• It is time ও It is high time এর পরে subject না এসে, কোন verb আসলে ঐ verb এর Infinitive form হবে। 
→ যেমন: It is high time to change our attitude.

Example Sentence:
1. It is high time we changed our attitude.
2. It is high time we addressed the environmental issues affecting our community.

Source: A Passage To The English Language: S. M. Zakir Hussain.