And in addition what @Tungbulu has said.
First of all, let me quickly correct an impression, the purpose of being aggressive isn't necessarily to maximize on short term gains or "to see good gains" as you put it, the main purpose of investors being aggressive should be reach their long term goals faster and not to capitalize on short term gains.
Now Usually every investor is meant to invest with their discretionary income, in a situation where an investor due to much eagerness to reach their goals faster, decides to invest with all their Emergency funds, rather than just a fraction or percentage of it, they're being aggressive enough, and this level of aggressiveness could still be arguably considered to be reasonable, but when folks starts feeling like their discretionary income isn't enough to help them reach their goals faster, and then they opt for other means, like taking loans and/or even using funds meant for some other purposes, then that's IMO definitely being reckless and an unhealthy approach to building one's Bitcoin investment.
If a person uses emergency funds to buy aggressively, it will not be the right approach at all. As you said, at the end of the investment stage. Even at the end of building your portfolio, if you buy with emergency funds, it will not be the right approach at all. Because your time is not over yet. If you face any financial disaster during this time, how will you deal with this financial crisis? So investing with emergency funds will never be the right decision.
You should be aggressive depending on your financial situation. If you are not aggressive depending on your financial situation, then you may face big risks after a while. For example, if you invest with the money you need, then you will have to sell your holdings or take a loan from someone. So it is always best to be aggressive depending on your financial situation.
Buying bitcoin with an emergency fund is never a good approach, it's like a misplaced priority and at some point the investor would likely touch what they're holding to solve issues that might arise, cause that's the function of the emergency funds, to settle uncertain circumstances that may arise in the future and if investor use it to accumulate aggressively and unexpected issues suddenly arises then they'll definitely withdraw what they're holding to solve it.
Every investor is meant to do it according to their financial status, therefore they should know when to be aggressive and when not to, you don't go aggressively cause your friend is doing so, the friend might be in a better situation to do so and if you're not there's no need going against what Bitcoin investment is all about just cause you want to accumulate more of it.