It is very disappointing when your plans get blown to the shithouse.
The thing is, this is not something where trying harder, getting over it or sucking it up will make a difference. If it makes you sick and tired, it makes you sick and tired.
We all hope we will be one of the exceptions who retains a degree of normal through chemo. I pulled that off during BC version 1 in 2006. BC version 2 has knocked the stuffing out of me.
Go easy on yourself. If you have to go to Plan B, just do it before you end up being forced to. You don't need to give up, just acknowledge that you are in a complicated situation where being strong, fit and determined may not make that much difference. Give yourself permission to make concessions and don't feel bad about it. Keep plodding. Mxxx