This is my primary objective as of late.
if you are generally not that smart at everything,
1) acknowledge it to yourself
2) try to rely on knowledgeable smart people who don't have a financial or emotional incentive to exploit you when providing advice
#2 can be really hard
i've seen sometimes people stumble with this because they can't discern who is smart and just rely on authority. someone i met once who was a crack smoker and extremely religious would often be in bad situations because he would take the advice of both preacher and government and trying to follow everyone, and sometimes the advice was bad and alienated people. just because someone has a degree doesn't mean they are smart. just because they are in authority doesn't mean they are smart.
sometimes, you can ask other smart people if the expert is good. or check to see how you can determine if someone is an expert and good.
i feel like this is an issue for even smart people or people of average intelligence. it can be very difficult to discern between people who both have credentials, especially if one of them is willing to tell you what you want to hear to financially exploit you in desperate times. the fact that someone has credentials, and is possibly even approved by the government to provide advice, does not always mean they are good.
generally, a good approach is to look for specifics of credentials: does this person have peer-reviewed research? where did they go to school and how hard is it to get in (which is usually an indication of intelligence)? does the person have a track record of successful results that is more than just one or two isolated incidents?
Some of the worst mistakes in life involved not listening to highly intelligent advisors. Depression also makes it much harder to do these things because when depressed, it's easier to slip into fantasy, not care about the future, and just hope that things will work out.
If you are thinking you are not intelligent, and genuinely are not (low IQ tests, low test scores, etc), that's a great thing because the world needs more unintelligent people who recognize they are unintelligent, as long as they can understand enough science to discern which experts to follow. This is actually one of the core problems in society.
With global warming, you have many below average intelligence people and middle intelligence people not able to discern which experts on global warming are correct, and also listening to religious teachings that are just lies, and can't really discern what is most accurate and important to recognize as true. The result is many people vote based on religious prejudices over their economic and environmental interests, and it's such a problem that it could end up destroying the entire planet from environmental destruction.
if you are trying to cope with being of low intelligence, congratulate yourself for being among the wise people of lower IQ who recognizes the issue and just do your best to get wise advice from higher IQ people.
then, once you realize you are low or middle range IQ, find out what you want out of life, or what you don't want, and read what experts have to say about how to get there. take a practical approach to getting what you want. do you want money? don't persue high iq professions that will waste time and cost money if you can't get past the IQ barrier to succeed in the profession (ie, don't try to get a physics degree if you have an IQ of 100). Instead, if you have an IQ of 100, don't go to college, get that air conditioner repair training, and then live substantially below your means and invest, invest, invest. Keep your costs low as possible, budget, use the power of math (even if you aren't great at math yourself), and find other ways to get income.
Also remember that IQ is all relative to other IQs. If you have an IQ of 100, you are so, so, so much smarter than someone with an IQ of 85, and if you have an IQ of 85, then you are doing better than someone with a 115 who thinks they understand things better than experts.
Knowing your limits is really the best way to do well, being realistic and pragmatic, then following advice from people who excel in areas you are not great at. There may be things you can be great at, so figure out what those things are, and do those things, if possible.