自己 literally means "self" so you can think of it as being used in the same way as "myself" is used in English. If we wanted to translate these sentences, one way to do it would be like this: 我觉得I think... 我自己觉得 I myself think...
Alternatively: 我觉得 In my opinion.... 我自己觉得 In my personal opinion...
In this case, 调动 means to mobilize or activate. 起来 literally means to come up, but you can think of it as to start. Thus, you can translate the sentence this way: 我自己觉得,个人的主观能动性真正是充分调动起来了。
In my personal opinion, it truly and fully activates each person's subjective initiative.