Robin Williams was committed to four film projects at the time of his death, and feared the effect of the workload on his mental health.
A friend, who wished to remain anonymous, told the Telegraph that his high-intensity performances left the star drained.
"Robin had promised himself he would not do any more as he invested so much in his roles that it left him drained and particularly vulnerable to depressive episodes.
"He signed up to do them purely out of necessity. He wasn't poor, but the money wasn't rolling in any more and life is expensive when you have to pay off two ex-wives and have a family to support."
Amongst the films was a sequel to 1993 hit Mrs Doubtfire.
The cancellation of his TV sitcom The Crazy Ones after just one season, lead to him to taking up more film work.
As well as reprising his role as a nanny Mrs Doubtfire, Williams was working on Night at the Museum: Secret of the Tomb; Merry Friggin Christmas, a seasonal comedy due out in November; drama Boulevard, and science-fiction comedy Absolutely Anything.
The 63-year-old was found dead at his home in Tiburon, California, on Monday. He is believed to have hung himself.
Williams had recently sold his California ranch, and there was speculation that he was experiencing money problems.
"There are bills to pay. My life has downsized, in a good way. I'm selling the ranch up in Napa. I just can't afford it anymore," he told Parade magazine.