Student or Learner
This is pretty much of a philosophical writing, and what does "a person" mean? The person who commits suicide or another person other than him? If it is another person, it probably means "the suicider has been using others as a means to his life, but when things don't work out as he wants, he tries to give up his life". Otherwise, it would mean "he has been using himself". Anyway, both the supposition don't come to my mind.
ex)For Kant, respect for autonomy entails duties to oneself as well as others, most notably the duty to treat humanity as an end in itself. This duty constraints the way a person can treat himself. According to Kant, murder is wrong because it uses the victim as a means rather than respects him as an end. But the same can be true of suicide. If a person does away with himself in order to escape from a painful situation, he is making use of a person merely as a means to maintain a tolerable state of affairs till the end of his life...
Okay, I got it, then what does this mean? He(suicidal person) is using himself to get away from pain or what?
"as a means to maintain a tolerable state of affairs till the end of his life"
-? He has decided that life is no longer 'a tolerable state of affairs'.
(Note that there is a typo in your original text. The verb is 'constrain'. That which constrains imposes a constraint.)