MIT puts more emphasis on the quality of implementations than most schools do, but there is much variation even within this lab. One consequence of this is that you can't please all the people all the time. Another is that you may often be unsure yourself whether you've made progress, which can make you insecure. This is normal. Keep correcting it with feedback from other people.
Several things can help with insecurity about progress.
More important, probably, is talking to as many people as you can about your ideas and getting their feedback. For one thing, they'll probably contribute useful ideas, and for another, some of them are bound to like it, which will make you feel good. Since standards of progress are so tricky, it's easy to go down blind alleys if you aren't in constant communication with other researchers. This is especially true when things aren't going well, which is generally the time when you least feel like talking about your work. It's important to get feedback and support at those times.