Should I book profit every time when market is at peak?

Dear Sir,

I want to know about the mutual fund strategy.

1. If my view is long term and I kept my sip investment till 20 years instead of booking profits at regular interval when market is at peak,but due to cyclic nature of market ,my investment plus profit remains average or less in the end when market is at bottom.

Now my question is:

1.Will i get the power of compounding? How?

2.Should i watch and book profit every time when market is at peak?

3.Your best strategy?