Well now, how-how do you fit into this whole thing? ---《老友記》 第一季 第二集
你现在要怎么办?
fit into
适应，符合
例句:
Machines have been developed that could produce hundreds, even thousands, of identical parts that would fit into place where the broken puts were completely.
能够生产几百乃至几千个可互换的零件的机器研制出来了，这些可互换的零件完全适合于损坏了的零件的位置。
Taper the plug off a bit with the chisel so that it will fit into the hole.
用凿子把塞子的一头削掉一点，使它能塞进洞里。
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关于问题补充：
stop doing是停止当前做的事
stop to do 是停止了当前做的事去做另一件事
我不懂这和你的问题有什么关系……
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顺便说说fit:
作adj.:
A be fit for B "A适合B"
.........to do B
作v.：
fit sth into sth
find or have sufficient space or room for sth in a place 找到或尚有足够的地方容纳某物:
We can't fit any more chairs into the room. 房间里没有地方多放椅子了.
This card just fits nicely into that envelope. 这张卡片正好能装进那个信封里.
……
唉，说实话，我当时学时就记住了2个用法：
A be fit for B = B fit A