The former RNID chief executive also called for a major shake-up of charity regulation and governance structures during his plenary speech at CAF's annual conference last week.
Strachan warned that a culture of whingeing and complaining could be damaging the way that the sector is perceived.
"There are many people in politics who wouldn't stand up and say it, but who are really thinking that the voluntary sector moans and whinges and 'can't-do'," he said. "It is our job to show that we can do."
Strachan insisted that the sector must make more effort to promote its strengths and prove its effectiveness to government, funders and the public.
"We spend a lot of time whingeing, and there is often the view that the rest of the world owes it to us," he said. "We need to explain what value we can add and the skills that others want to work with."
Strachan, who continues to work for the RNID as chair of the board of trustees, called for an overhaul of regulatory and governance practices in order to make the sector more efficient and improve the way it is viewed.
He called for the red tape strangling smaller charities to be cut back and suggested that the Charity Commission should consider relinquishing responsibility for awarding charitable status to smaller organisations.
This role, he said, could be assumed by another government body, such as the Inland Revenue.
These changes could pave the way for greater regulation of the top 200 charities, which Strachan believes is long overdue. He also added his voice to the recent debates that have been reverberating around the sector about reforms that would allow chief executives to sit on trustee boards.
"It is absurd not to have chief executives on trustee boards - in most cases they sit at the table anyway," he said. "They may not be able to vote, but they tacitly smile or grimace as appropriate."
He also believes that chairmen should be paid.
"To have someone doing such a job as an afterthought or on their lunch break from their day job is ridiculous. It leaves the task to those who are rich, or those who do not necessarily have the appropriate skills."
Strachan admitted that there is no panacea to the problems facing the sector, but insisted that better governance and regulation is at the heart of regaining public trust and confidence.
"We need to be well governed and well managed and determined to change the world."
See CAF Conference News, page 3.