To be sure, neglecting to reduce your agreement to writing isn't a good thing. And certainly, in hindsight you can easily wonder how you let that happen.
But thinking those thoughts aren't terribly productive, and won't solve anything.
On the other hand, you should know that just because you failed to reduce your agreement to writing doesn't necessarily mean that you are completely without legal recourse. There are some circumstances where a plaintiff can still recover his or her damages flowing from a breach of contract. (For more on this topic, please see the free e-book, "When You Don't Have a Written Agreement").
One such example is in the context of an agreement for the sale of goods, which normally does have to be reduced to writing. In that context, a contract needs to have the following essential terms in order to be considered an enforceable agreement under New York law: (1) quantity; (2) price; and, (3) time and manner of delivery. However, New York's courts have also explictly held that "[T]he fact that one or more of these terms is left open is not fatal."
That's where e-mail comes in.
According to one of New York's Federal Courts, even if one of those terms is missing, an e-mail confirming the parties' oral agreement may suffice to fill in the gaps. See, Bazak Int'l Corp. v. Tarrant Apparel Grp., 378 F.Supp.2d 377, 389-90 (S.D.N.Y. 2005) (Marrero, D.J.) (e-mail confirming oral agreement created issues of fact concerning whether parties intended to be bound).