Fundstrat's Thomas Lee said on Wednesday that he has "definitely been too cautious" on the bull market rally so far.
In an interview with CNBC's "Fast Money Halftime Report," Lee said that the rally's strength reflects optimistic expectations of growth and new investors entering the market.
"I think the resilience is really highlighting when you get [out] from the Fed put [option] and you start thinking about pro-growth and how underinvested people are, this is what's really powering the market," Lee said.
A put option contract gives its owner the right to sell a specific portion of an underlying asset such as a stock at a predetermined price at a set time.
Lee also said he was reassured that his system of buying CRAP — stocks related to computers, resources, American banks and phone carriers — has served him through the rally.
"It's the cyclical stocks, and really it's been led by tech and financials, which [are] really the groups we like," the strategist said.
In a January interview with CNBC, Lee came out slightly bearish on financial stocks, cautioning that they may be overextended on hopes of loosened regulations.
Lee pointed out that there are still areas where the market has not fully embraced upticks in the economy that are fueling parts of the rally.
"I think the underlying economy is actually picking up a lot of momentum. And remember, we had an industrial recession for four quarters that's essentially over. But [a] good economy doesn't have to mean great stocks," Lee said.
"That's maybe where we're getting a little stuck, because the bond market isn't really embracing this upturn as readily as the equity markets," he continued. "The yield curve is still flat. It's actually been flattening."
Following that, the rally may not necessarily mean that spirits will remain high, according to Lee.
"I think we're entering a period where it's a policy put over a Fed put, and that's why we kind of [expect] choppier markets," the strategist said.