Advantages and disadvantages of self-assessment

Self Assessment
The usage of self assessment would come really in handy when it comes to language learning because it helps the student and the teacher as well, to notice the level of performance he/she has had through the course. It also helps to notice and understand the possible mistakes he/she has made and how to correct them. But self assessment does not only take in notice the mistakes, it also helps the student to see his/her progress in reading, writing, speaking, listening, vocabulary, pronunciation, etc., and how much practice did it took to get where he/she is right now. 

Advantages
Profiles/Learner Diaries/Counseling sessions:
Ss’ are asked to do these types of self-assessment they really have the opportunity reflect and write/speak freely what they think they have learned along the course and what they haven’t.
Rating/Graph/Adjectives:
Ss’ rate themselves with numbers or with adjectives. This is really easy to graphic and to grade (as a teacher).
Self-editing/Correction:
Ss’ get the opportunity to look at their own mistakes, or their peers’, and correct them. This gives them the opportunity to reflect on them and practice the language while helping others.
Questionnaires: 
(listing, ranking performance/problems, multiple choice questions, agreeing/disagreeing, short answer questions)
All of the above help the teacher know more about the Ss’ production along the course, knowledge of vocabulary and grammar, and comprehension of both the questions and the answers given.

Disadvantages
Profiles/Learner Diaries/Counseling sessions:
Using these types of self-assessment would take a lot of time to read each of them. This would work better with small groups.
Rating/Graph/Adjectives:
Ss’ can easily rate themselves with an excellent performance in order to get a good grade. 
Self-editing/Correction:
Ss’ can cheat on the number of mistakes they had and say they did not have any from the start. They can do the same for their peers.
Questionnaires: 
(listing, ranking performance/problems, multiple choice questions, agreeing/disagreeing, short answer questions)
Some Ss’ may only answer these questionnaires randomly in order to finish with the task without even reading it. This decreases the reliability and credibility of the purpose of self-assessment.