The most important question is, "DO YOU WANT TO GO INTO TEACHING?" IF THE ANSWER IS YES, THEN DO THE PLACEMENT, making sure that you get as much help as possible. Do you know your areas of difficulty? If not find out and get help and make sure that you address the problems. Was there a particular problem connected with the school you were placed in and if so are you being offered a placement in a different school? If not, and you don't feel that you will succeed in that particular school then see if you can negotiate a transfer or ask a sympathetic tutor (personal tutor?) to intervene on your behalf. Be prepared to work very hard. Ask yourself, honestly, if you worked hard enough the first time (the answer may well be yes). If you want to teach then it is worth putting yourself through it. 40 days is not a long time in your life. (I have recently retired after more than 30 years in teaching, the latter part of the time as a primary headteacher.)
IF YOU DO NOT WANT TO TEACH DON'T REDO THE PLACEMENT except it may still be worth having a go just to gain the qualification which could possible be useful in a different job context.
Are you working with primary or secondary pupils and which Key Stage or age group? If you are willing to give a brief indication of your problems then other people may be able to offer more specific advice if you think that would help.
I know someone who had to completely redo their final teaching placement, which they did successfully and very quickly found a permanent teaching post. So you are not alone and it can be done.
Think positively and good luck with whatever you decide to do. Hope this helps a little.