In a recent appraisal I was told that others see me as weak and ineffectual because of this, and it's apparently held me back over the years. How can I stop this without radically altering who I am?
There seem to be two parts to your conundrum: the question of whether you do in fact have differing views from your boss and others on what should be happening in your organisation, and the issue of whether you choose to express these views or not.
If you have unexpressed opinions, based on your experience and insight, you are holding back a valuable commodity from your company and it will be important for your own satisfaction and for the quality of your work that you find a way of expressing these views. It's also unlikely that your boss is always right, and having input from someone with a different point of view will help you all reach better decisions, through broader understanding.
Does your compliant stance carry over into your home life? Do you always agree with what your partner or friends want to do, even if it's not what you believe to be right? Possibly not: we can be highly capable in one part of our life but overwhelmed in another.
If you do speak your own mind outside work, it's worth capturing that mindset of how you feel and what you look and sound like when you offer a contrary opinion, and taking it with you mentally to your next big meeting so you can experiment with replicating it there. Even if at first you rehearse it only in your head (eg, 'I'd make this point now, if I was speaking my mind'), you will be readying yourself for the next chapter of your working life.
However, some people are tractable and avoid confrontation all their lives. This type of behaviour often stems from childhood and may have had self-preservatory origins - being 'good' is the safest way to be.
If this is the case, it could be time to reconsider whether this behaviour is as useful to you now as it may once have been. Deepak Chopra has christened this phenomenon 'premature cognitive commitment', the adoption of beliefs or behaviours at a young age without examination, a sort of pre-conditioning that we may need to question as our lives unfold and our needs and aspirations change.
To start the process, try unpacking the issue. Ask yourself what is the worst thing that could happen if you publicly disagreed with your boss, or other figures of authority. Naming our unspoken fear is a good way of reducing its scariness. Also, try to work out what you gain from not disagreeing: does your boss respect you more? Do you get your own way privately?
Reluctance to speak up for what we believe in is often deep-rooted in low self-esteem; we don't feel worthy of having our own opinions. This pattern can stick with us long after we've started to achieve some success, and the outside world can see no evidence that we are not solid citizens, more than competent to do our jobs.
All habits are hard to break, and self-denigration is no exception. Successful behaviour shifts usually require four things. The first three elements are knowledge of what you'd like to achieve; an understanding of why it matters (to you, principally, and to others); and positive experience of doing things differently. The fourth prerequisite is time. You are unlikely to transform overnight, but set some markers now for where you'd like to be in, say, three months, and find interim indicators to tell you are making progress (for example, disagreeing outside the meeting, one-to-one with your boss).
That way, each time you speak out and the ground doesn't open to swallow you, you know you are one step further along your journey. This in itself will help your self-esteem: you made a commitment to yourself and you are honouring it.
Stevie Spring is the highly competent CEO of Clear Channel, but confesses to having suffered from the well-documented 'impostor' syndrome at a much earlier stage in her life. This was the feeling that any moment she would be found out as not really up to the job. Now she says: 'I can look myself in the mirror and know I am genuinely good at what I do, and not an impostor at all.'
Perhaps feeling this confident about your abilities seems an impossible challenge at this point, but in recognising the need to change, you are starting on a road that could lead to a happier state.