Example: "I like reading books and love to swim" or "I like reading books and I love to swim"
Short answer: Both are natural.
Long answer: Repeating the subject usually means there is something you want to emphasize.
For example, "I like reading and I love to swim,"
...lets the listener feel like you are a person of many interests and hobbies,
...whereas "I like reading and I love to swim,"
...lets the listener know that you have these two hobbies, but you care for the latter more passionately.
Does this help?
Both forms are grammatical and idiomatic. In short clauses, omitting repetitions of the subject leads to a clause that is both concise and easily understood. However, in lengthy clauses, where verbs are separated by one or more phrases or subordinate clauses, omitting repetitions of the subject may lead to a clause that is very hard to interpret. So, as general rule of style that undoubtedly has exceptions, I'd tend to omit repeatitions of the subject for verbs that are close together, but repeat the subject for verbs that are separated by multiple phrases or any subordinate clause.