A few points:
1) Personally, I would use a colon after the word "canvas" for more emphasis.
2) I would replace the "&" symbol with a comma.
3) I would place an "and" after this comma, and remove the comma from after the word "it".
4) I would remove the word "it" from the sentence "Art is not inherited but is a science..." Also, remove the speech marks and capitals from the word "ART".
5) You may want to remove the comma before the word "which (has to be mastered..."
6) Remove "we" before "at celebrity management..." and capitalize "At" as the start of the sentence.
7) I'm not sure if "celebrity management" is the name of a company or organization. If so, you want to use capitals, such as Celebrity Management.
8) If "National Celebrity Management Agency" is not a name of an organization, then you want to remove the capitals from these words.
9) At "we are" before "dedicated to..."
10) Don't capitalize the "c" in "clients".
11) Remove "the" before "India".
12) Add a comma after "India", and replace, and remove the brackets on "and abroad".
13) Remove "firmly believe in it".
14) Don't capitalize "p" in "paint".
Here is what I would use:
Life is your canvas: no one can paint it but you, and how you paint it is the art. Art is not inherited but is a science which has to be mastered over a period of time; it is the accumulation of expertise and experience. At Celebrity Management, an exclusive national celebrity management agency, we are dedicated to providing talent to our clients throughout India, and abroad. We paint our passion with all colours of success.
Note: I am not an English teacher.
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