This question relates to an 'age-old' philosophical question - can we change the future? are you confined by your destiny? can you change your fate?
Remember that this poem was 'adapted' for a Christian audience from the original Pagan version. The line of the poem "fate is stronger/... than any man's mind? " tells the reader that God (or gods) are omnipotent, solely determining your unchangeable fate.
The Seafarer may be a exemplum - that is, a piece of writing written for the purpose of 'lecturing' the audience on particular point - here focused on the Anglo-Saxon belief that Fate controls mortal lives. And then reinforcing that the Christian God is also all-powerful.
Indeed "Fate" appears as a character in the poem - as if Fate just decides to give sickness, war or death to people in a haphazard fashion.
In order to answer the question "do you agree", you will need to look at your own beliefs and faith. Do random events control the flow of your life, or a God (or gods), or are you in control of your life plan?
Chances are your answer will include a mixture of 'yes/no' points. For example: if you work hard you'll get better grades, but some people are naturally better at some school subjects. Or, if you're hit by a car, is that the fault of 'God' or just bad luck?