My cofounder is planning to quit , we have a preseed termsheet in place

He is a red flag. Not the kind of partner you want to build with. Building is hard itself, why complicate it by building it with someone who isn't as crazy as you about the future? I've been a 2 time founder with over 6 years of entrepreneurial experience, happy to chat :)

It is not an easy decision. I have similar friends whom I have to motivate time and again, but deep down I know we aren't compatible through I want to enjoy my startup journey with him as his is my childhood friend and understand me. If you like, share your startup vision and idea at larp.web4.@gmail.com, I will be able to help for free. I understand the pain.

This happens all the time,your friend must have thought a lot before making his mind and now,it will just be waste of time if you're trying to convince.let him go,buy his shares and find someone to fill up his space - not necessary a co founder and run the show alone.we all are capable of more than we think.all the best

Do you guys have a Founder's agreement in place?

Hey - would you be open to connect. In a similar position but we have already raised our round and are at the verge closing the company( still have 70% of the money in bank)

He may have some personal commitments to meet which he may not be able to do so, maybe try and figure that out and solve for that.

Just have an honest chat with him and respect his decision thereafter. Sometimes all the other person needs is someone to talk to. If he has already given up better to part happily rather than treating him as a redflag. If he has thought through it and does not have the will anymore nothing will help.
I will actually commend him for saying no when you have a 'good' event of funding and calling it at that point in time.

It depends on how much you need them.

this is a deeply personal question and honestly nobody who doesn't know both of you well can help.

all I can say is - better you found out now than after the signing.

and he's right about the constant disappointments. most ppl I know take minimum 2 years to even get a sense of whether the venture will survive, 5-6 to start making money. I failed at multiple ventures for nearly a decade before making money.

First and foremost you have to decide if you want to continue with your startup or not. If yes, then Have a chat with your investors and ask them if they will still back you if the other founder will leave. Sometimes the VCs are hesitant to tell you upfront but they may be backing one founder more than the other and if that founder is you, they will gladly back you even if the other guy will leave. The good part of all this is that you will be having larger stake in the company which is going to help you immensely later in the funding rounds.